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	$134.92	4.312%	$140.7378	$140.74	$140.75	$140.70
Purchase #2	$48.89	12.188%	$54.8487	$54.85	$54.85	$54.80
Purchase #3	$196.46	5.674%	$207.6071	$207.61	$207.60	$207.60
Purchase #4	$142.83	9.387%	$156.2375	$156.24	$156.25	$156.20
Purchase #5	$203.65	9.846%	$223.7014	$223.70	$223.70	$223.70
Purchase #6	$129.31	10.246%	$142.5591	$142.56	$142.55	$142.60
Purchase #7	$124.83	10.651%	$138.1256	$138.13	$138.15	$138.10
7 purchase totals =	$980.89		$1,063.8172	$1,063.83	$1,063.85	$1,063.70