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	$174.40	8.112%	$188.5473	$188.55	$188.55	$188.50
Purchase #2	$37.65	11.240%	$41.8819	$41.88	$41.90	$41.90
Purchase #3	$209.32	11.391%	$233.1636	$233.16	$233.15	$233.20
Purchase #4	$243.58	8.747%	$264.8859	$264.89	$264.90	$264.90
Purchase #5	$141.31	3.625%	$146.4325	$146.43	$146.45	$146.40
Purchase #6	$60.61	5.303%	$63.8241	$63.82	$63.80	$63.80
Purchase #7	$201.84	5.198%	$212.3316	$212.33	$212.35	$212.30
7 purchase totals =	$1,068.71		$1,151.0669	$1,151.06	$1,151.10	$1,151.00