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	$233.98	3.658%	$242.539	$242.54	$242.55	$242.50
Purchase #2	$95.73	4.135%	$99.6884	$99.69	$99.70	$99.70
Purchase #3	$177.35	6.824%	$189.4524	$189.45	$189.45	$189.50
Purchase #4	$113.77	7.803%	$122.6475	$122.65	$122.65	$122.60
Purchase #5	$173.91	9.674%	$190.7341	$190.73	$190.75	$190.70
Purchase #6	$157.74	9.370%	$172.5202	$172.52	$172.50	$172.50
Purchase #7	$124.50	11.613%	$138.9582	$138.96	$138.95	$139.00
7 purchase totals =	$1,076.98		$1,156.5398	$1,156.54	$1,156.55	$1,156.50