Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$162.50	5.850%	$172.0063	$172.01	$172.00	$172.00
Purchase #2	$116.76	11.732%	$130.4583	$130.46	$130.45	$130.50
Purchase #3	$162.89	7.703%	$175.4374	$175.44	$175.45	$175.40
Purchase #4	$159.96	7.527%	$172.0002	$172.00	$172.00	$172.00
Purchase #5	$166.83	6.451%	$177.5922	$177.59	$177.60	$177.60
Purchase #6	$110.28	6.550%	$117.5033	$117.50	$117.50	$117.50
Purchase #7	$175.74	12.790%	$198.2171	$198.22	$198.20	$198.20
7 purchase totals =	$1,054.96		$1,143.2148	$1,143.22	$1,143.20	$1,143.20