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	$130.98	12.276%	$147.0591	$147.06	$147.05	$147.10
Purchase #2	$47.73	10.454%	$52.7197	$52.72	$52.70	$52.70
Purchase #3	$151.37	9.401%	$165.6003	$165.60	$165.60	$165.60
Purchase #4	$138.52	6.739%	$147.8549	$147.85	$147.85	$147.90
Purchase #5	$43.61	12.717%	$49.1559	$49.16	$49.15	$49.20
Purchase #6	$67.36	6.639%	$71.832	$71.83	$71.85	$71.80
Purchase #7	$213.95	6.399%	$227.6407	$227.64	$227.65	$227.60
7 purchase totals =	$793.52		$861.8626	$861.86	$861.85	$861.90