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	$178.58	5.406%	$188.234	$188.23	$188.25	$188.20
Purchase #2	$44.45	8.585%	$48.266	$48.27	$48.25	$48.30
Purchase #3	$204.63	6.451%	$217.8307	$217.83	$217.85	$217.80
Purchase #4	$162.47	12.570%	$182.8925	$182.89	$182.90	$182.90
Purchase #5	$98.66	6.733%	$105.3028	$105.30	$105.30	$105.30
Purchase #6	$36.32	5.500%	$38.3176	$38.32	$38.30	$38.30
Purchase #7	$134.33	13.528%	$152.5022	$152.50	$152.50	$152.50
7 purchase totals =	$859.44		$933.3458	$933.34	$933.35	$933.30