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	$69.93	4.197%	$72.865	$72.87	$72.85	$72.90
Purchase #2	$104.85	11.507%	$116.9151	$116.92	$116.90	$116.90
Purchase #3	$172.51	3.281%	$178.1701	$178.17	$178.15	$178.20
Purchase #4	$100.47	3.434%	$103.9201	$103.92	$103.90	$103.90
Purchase #5	$199.71	8.613%	$216.911	$216.91	$216.90	$216.90
Purchase #6	$32.85	7.840%	$35.4254	$35.43	$35.45	$35.40
Purchase #7	$209.38	9.872%	$230.05	$230.05	$230.05	$230.10
7 purchase totals =	$889.70		$954.2567	$954.27	$954.20	$954.30