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	$205.79	9.435%	$225.2063	$225.21	$225.20	$225.20
Purchase #2	$91.35	8.135%	$98.7813	$98.78	$98.80	$98.80
Purchase #3	$156.37	13.453%	$177.4065	$177.41	$177.40	$177.40
Purchase #4	$161.54	6.511%	$172.0579	$172.06	$172.05	$172.10
Purchase #5	$133.51	10.200%	$147.128	$147.13	$147.15	$147.10
Purchase #6	$180.59	4.192%	$188.1603	$188.16	$188.15	$188.20
Purchase #7	$40.75	3.429%	$42.1473	$42.15	$42.15	$42.10
7 purchase totals =	$969.90		$1,050.8876	$1,050.90	$1,050.90	$1,050.90