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	$243.91	7.706%	$262.7057	$262.71	$262.70	$262.70
Purchase #2	$244.47	4.491%	$255.4491	$255.45	$255.45	$255.40
Purchase #3	$229.34	3.700%	$237.8256	$237.83	$237.85	$237.80
Purchase #4	$248.83	6.287%	$264.4739	$264.47	$264.45	$264.50
Purchase #5	$205.59	7.767%	$221.5582	$221.56	$221.55	$221.60
Purchase #6	$166.88	11.116%	$185.4304	$185.43	$185.45	$185.40
Purchase #7	$171.80	7.251%	$184.2572	$184.26	$184.25	$184.30
7 purchase totals =	$1,510.82		$1,611.7001	$1,611.71	$1,611.70	$1,611.70