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	$45.79	6.263%	$48.6578	$48.66	$48.65	$48.70
Purchase #2	$233.27	9.266%	$254.8848	$254.88	$254.90	$254.90
Purchase #3	$10.86	8.443%	$11.7769	$11.78	$11.80	$11.80
Purchase #4	$210.76	13.327%	$238.848	$238.85	$238.85	$238.80
Purchase #5	$212.53	9.804%	$233.3664	$233.37	$233.35	$233.40
Purchase #6	$62.80	13.520%	$71.2906	$71.29	$71.30	$71.30
Purchase #7	$61.83	8.536%	$67.1078	$67.11	$67.10	$67.10
7 purchase totals =	$837.84		$925.9323	$925.94	$925.95	$926.00