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	$169.79	7.353%	$182.2747	$182.27	$182.25	$182.30
Purchase #2	$247.52	10.640%	$273.8561	$273.86	$273.85	$273.90
Purchase #3	$30.71	5.347%	$32.3521	$32.35	$32.35	$32.40
Purchase #4	$74.84	4.331%	$78.0813	$78.08	$78.10	$78.10
Purchase #5	$152.99	3.395%	$158.184	$158.18	$158.20	$158.20
Purchase #6	$177.42	12.675%	$199.908	$199.91	$199.90	$199.90
Purchase #7	$83.90	11.434%	$93.4931	$93.49	$93.50	$93.50
7 purchase totals =	$937.17		$1,018.1493	$1,018.14	$1,018.15	$1,018.30