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	$155.54	6.485%	$165.6268	$165.63	$165.65	$165.60
Purchase #2	$84.64	13.123%	$95.7473	$95.75	$95.75	$95.70
Purchase #3	$123.98	7.427%	$133.188	$133.19	$133.20	$133.20
Purchase #4	$244.83	12.574%	$275.6149	$275.61	$275.60	$275.60
Purchase #5	$216.40	4.661%	$226.4864	$226.49	$226.50	$226.50
Purchase #6	$218.43	5.276%	$229.9544	$229.95	$229.95	$230.00
Purchase #7	$56.36	6.262%	$59.8893	$59.89	$59.90	$59.90
7 purchase totals =	$1,100.18		$1,186.5071	$1,186.51	$1,186.55	$1,186.50