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	$95.94	9.504%	$105.0581	$105.06	$105.05	$105.10
Purchase #2	$230.85	4.263%	$240.6911	$240.69	$240.70	$240.70
Purchase #3	$69.93	11.362%	$77.8754	$77.88	$77.90	$77.90
Purchase #4	$56.29	6.621%	$60.017	$60.02	$60.00	$60.00
Purchase #5	$63.63	13.603%	$72.2856	$72.29	$72.30	$72.30
Purchase #6	$249.28	11.141%	$277.0523	$277.05	$277.05	$277.10
Purchase #7	$160.68	5.380%	$169.3246	$169.32	$169.30	$169.30
7 purchase totals =	$926.60		$1,002.3041	$1,002.31	$1,002.30	$1,002.40