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	$40.50	4.461%	$42.3067	$42.31	$42.30	$42.30
Purchase #2	$123.49	6.495%	$131.5107	$131.51	$131.50	$131.50
Purchase #3	$18.73	9.825%	$20.5702	$20.57	$20.55	$20.60
Purchase #4	$62.98	7.406%	$67.6443	$67.64	$67.65	$67.60
Purchase #5	$86.27	8.773%	$93.8385	$93.84	$93.85	$93.80
Purchase #6	$31.47	4.331%	$32.833	$32.83	$32.85	$32.80
Purchase #7	$74.43	7.263%	$79.8359	$79.84	$79.85	$79.80
7 purchase totals =	$437.87		$468.5393	$468.54	$468.55	$468.40