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	$143.90	7.715%	$155.0019	$155.00	$155.00	$155.00
Purchase #2	$191.29	5.594%	$201.9908	$201.99	$202.00	$202.00
Purchase #3	$69.31	3.754%	$71.9119	$71.91	$71.90	$71.90
Purchase #4	$114.31	12.744%	$128.8777	$128.88	$128.90	$128.90
Purchase #5	$58.71	4.308%	$61.2392	$61.24	$61.25	$61.20
Purchase #6	$53.28	12.544%	$59.9634	$59.96	$59.95	$60.00
Purchase #7	$138.77	9.442%	$151.8727	$151.87	$151.85	$151.90
7 purchase totals =	$769.57		$830.8576	$830.85	$830.85	$830.90