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	$168.52	9.637%	$184.7603	$184.76	$184.75	$184.80
Purchase #2	$9.51	8.596%	$10.3275	$10.33	$10.35	$10.30
Purchase #3	$109.63	9.508%	$120.0536	$120.05	$120.05	$120.10
Purchase #4	$99.89	11.370%	$111.2475	$111.25	$111.25	$111.20
Purchase #5	$79.98	11.389%	$89.0889	$89.09	$89.10	$89.10
Purchase #6	$147.66	3.526%	$152.8665	$152.87	$152.85	$152.90
Purchase #7	$52.42	3.550%	$54.2809	$54.28	$54.30	$54.30
7 purchase totals =	$667.61		$722.6252	$722.63	$722.65	$722.70