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	$142.55	8.837%	$155.1471	$155.15	$155.15	$155.10
Purchase #2	$140.61	4.136%	$146.4256	$146.43	$146.45	$146.40
Purchase #3	$207.26	10.423%	$228.8627	$228.86	$228.85	$228.90
Purchase #4	$68.88	12.635%	$77.583	$77.58	$77.60	$77.60
Purchase #5	$235.63	3.505%	$243.8888	$243.89	$243.90	$243.90
Purchase #6	$99.33	4.120%	$103.4224	$103.42	$103.40	$103.40
Purchase #7	$124.72	8.659%	$135.5195	$135.52	$135.50	$135.50
7 purchase totals =	$1,018.98		$1,090.8491	$1,090.85	$1,090.85	$1,090.80