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	$115.98	12.215%	$130.147	$130.15	$130.15	$130.10
Purchase #2	$68.45	4.545%	$71.5611	$71.56	$71.55	$71.60
Purchase #3	$172.45	12.433%	$193.8907	$193.89	$193.90	$193.90
Purchase #4	$243.53	10.864%	$269.9871	$269.99	$270.00	$270.00
Purchase #5	$97.66	10.832%	$108.2385	$108.24	$108.25	$108.20
Purchase #6	$189.43	9.811%	$208.015	$208.02	$208.00	$208.00
Purchase #7	$55.72	6.354%	$59.2604	$59.26	$59.25	$59.30
7 purchase totals =	$943.22		$1,041.0998	$1,041.11	$1,041.10	$1,041.10