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	$221.32	11.127%	$245.9463	$245.95	$245.95	$245.90
Purchase #2	$18.90	9.467%	$20.6893	$20.69	$20.70	$20.70
Purchase #3	$101.44	9.496%	$111.0727	$111.07	$111.05	$111.10
Purchase #4	$92.84	12.470%	$104.4171	$104.42	$104.40	$104.40
Purchase #5	$156.75	5.473%	$165.3289	$165.33	$165.35	$165.30
Purchase #6	$51.97	8.624%	$56.4519	$56.45	$56.45	$56.50
Purchase #7	$146.38	12.810%	$165.1313	$165.13	$165.15	$165.10
7 purchase totals =	$789.60		$869.0375	$869.04	$869.05	$869.00