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	$165.55	3.401%	$171.1804	$171.18	$171.20	$171.20
Purchase #2	$66.58	3.814%	$69.1194	$69.12	$69.10	$69.10
Purchase #3	$185.41	5.788%	$196.1415	$196.14	$196.15	$196.10
Purchase #4	$139.79	13.405%	$158.5288	$158.53	$158.55	$158.50
Purchase #5	$221.36	4.375%	$231.0445	$231.04	$231.05	$231.00
Purchase #6	$135.79	9.119%	$148.1727	$148.17	$148.15	$148.20
Purchase #7	$179.56	7.322%	$192.7074	$192.71	$192.70	$192.70
7 purchase totals =	$1,094.04		$1,166.8947	$1,166.89	$1,166.90	$1,166.80