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	$159.87	13.699%	$181.7706	$181.77	$181.75	$181.80
Purchase #2	$159.94	13.565%	$181.6359	$181.64	$181.65	$181.60
Purchase #3	$182.28	7.778%	$196.4577	$196.46	$196.45	$196.50
Purchase #4	$211.43	6.530%	$225.2364	$225.24	$225.25	$225.20
Purchase #5	$193.68	7.820%	$208.8258	$208.83	$208.85	$208.80
Purchase #6	$208.33	3.834%	$216.3174	$216.32	$216.30	$216.30
Purchase #7	$40.80	13.424%	$46.277	$46.28	$46.30	$46.30
7 purchase totals =	$1,156.33		$1,256.5208	$1,256.54	$1,256.55	$1,256.50