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	$227.67	7.138%	$243.9211	$243.92	$243.90	$243.90
Purchase #2	$61.69	6.222%	$65.5284	$65.53	$65.55	$65.50
Purchase #3	$19.60	3.217%	$20.2305	$20.23	$20.25	$20.20
Purchase #4	$129.40	13.123%	$146.3812	$146.38	$146.40	$146.40
Purchase #5	$32.44	9.267%	$35.4462	$35.45	$35.45	$35.40
Purchase #6	$246.31	9.348%	$269.3351	$269.34	$269.35	$269.30
Purchase #7	$245.90	4.582%	$257.1671	$257.17	$257.15	$257.20
7 purchase totals =	$963.01		$1,038.0096	$1,038.02	$1,038.05	$1,037.90