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	$81.90	10.816%	$90.7583	$90.76	$90.75	$90.80
Purchase #2	$246.33	7.513%	$264.8368	$264.84	$264.85	$264.80
Purchase #3	$148.72	11.359%	$165.6131	$165.61	$165.60	$165.60
Purchase #4	$113.56	5.393%	$119.6843	$119.68	$119.70	$119.70
Purchase #5	$28.47	3.569%	$29.4861	$29.49	$29.50	$29.50
Purchase #6	$199.78	13.864%	$227.4775	$227.48	$227.50	$227.50
Purchase #7	$162.87	6.868%	$174.0559	$174.06	$174.05	$174.10
7 purchase totals =	$981.63		$1,071.9120	$1,071.92	$1,071.95	$1,072.00