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	$139.98	9.214%	$152.8778	$152.88	$152.90	$152.90
Purchase #2	$56.76	8.185%	$61.4058	$61.41	$61.40	$61.40
Purchase #3	$135.35	11.527%	$150.9518	$150.95	$150.95	$151.00
Purchase #4	$244.83	7.191%	$262.4357	$262.44	$262.45	$262.40
Purchase #5	$57.41	7.731%	$61.8484	$61.85	$61.85	$61.80
Purchase #6	$138.84	10.217%	$153.0253	$153.03	$153.05	$153.00
Purchase #7	$191.54	13.675%	$217.7331	$217.73	$217.75	$217.70
7 purchase totals =	$964.71		$1,060.2779	$1,060.29	$1,060.35	$1,060.20