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	$70.61	8.115%	$76.34	$76.34	$76.35	$76.30
Purchase #2	$211.59	12.251%	$237.5119	$237.51	$237.50	$237.50
Purchase #3	$237.76	4.498%	$248.4544	$248.45	$248.45	$248.50
Purchase #4	$231.64	11.542%	$258.3759	$258.38	$258.40	$258.40
Purchase #5	$237.59	7.491%	$255.3879	$255.39	$255.40	$255.40
Purchase #6	$230.61	12.535%	$259.517	$259.52	$259.50	$259.50
Purchase #7	$92.59	7.665%	$99.687	$99.69	$99.70	$99.70
7 purchase totals =	$1,312.39		$1,435.2741	$1,435.28	$1,435.30	$1,435.30