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	$111.85	3.145%	$115.3677	$115.37	$115.35	$115.40
Purchase #2	$120.41	11.149%	$133.8345	$133.83	$133.85	$133.80
Purchase #3	$143.26	7.330%	$153.761	$153.76	$153.75	$153.80
Purchase #4	$167.59	10.684%	$185.4953	$185.50	$185.50	$185.50
Purchase #5	$97.47	12.837%	$109.9822	$109.98	$110.00	$110.00
Purchase #6	$80.62	6.206%	$85.6233	$85.62	$85.60	$85.60
Purchase #7	$168.59	10.274%	$185.9109	$185.91	$185.90	$185.90
7 purchase totals =	$889.79		$969.9749	$969.97	$969.95	$970.00