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	$35.54	4.597%	$37.1738	$37.17	$37.15	$37.20
Purchase #2	$244.54	10.760%	$270.8525	$270.85	$270.85	$270.90
Purchase #3	$31.75	11.683%	$35.4594	$35.46	$35.45	$35.50
Purchase #4	$71.47	8.803%	$77.7615	$77.76	$77.75	$77.80
Purchase #5	$211.80	10.406%	$233.8399	$233.84	$233.85	$233.80
Purchase #6	$222.31	8.507%	$241.2219	$241.22	$241.20	$241.20
Purchase #7	$97.25	8.736%	$105.7458	$105.75	$105.75	$105.70
7 purchase totals =	$914.66		$1,002.0548	$1,002.05	$1,002.00	$1,002.10