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	$186.66	5.121%	$196.2189	$196.22	$196.20	$196.20
Purchase #2	$203.26	9.417%	$222.401	$222.40	$222.40	$222.40
Purchase #3	$235.38	5.198%	$247.6151	$247.62	$247.60	$247.60
Purchase #4	$129.77	8.521%	$140.8277	$140.83	$140.85	$140.80
Purchase #5	$161.64	3.582%	$167.4299	$167.43	$167.45	$167.40
Purchase #6	$135.85	11.711%	$151.7594	$151.76	$151.75	$151.80
Purchase #7	$196.32	11.450%	$218.7986	$218.80	$218.80	$218.80
7 purchase totals =	$1,248.88		$1,345.0506	$1,345.06	$1,345.05	$1,345.00