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	$160.54	12.830%	$181.1373	$181.14	$181.15	$181.10
Purchase #2	$67.98	5.203%	$71.517	$71.52	$71.50	$71.50
Purchase #3	$25.39	12.205%	$28.4888	$28.49	$28.50	$28.50
Purchase #4	$166.42	13.173%	$188.3425	$188.34	$188.35	$188.30
Purchase #5	$93.35	13.445%	$105.9009	$105.90	$105.90	$105.90
Purchase #6	$223.33	4.230%	$232.7769	$232.78	$232.80	$232.80
Purchase #7	$216.51	4.690%	$226.6643	$226.66	$226.65	$226.70
7 purchase totals =	$953.52		$1,034.8277	$1,034.83	$1,034.85	$1,034.80