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	$192.74	6.208%	$204.7053	$204.71	$204.70	$204.70
Purchase #2	$119.81	5.281%	$126.1372	$126.14	$126.15	$126.10
Purchase #3	$109.82	10.399%	$121.2402	$121.24	$121.25	$121.20
Purchase #4	$86.59	13.693%	$98.4468	$98.45	$98.45	$98.40
Purchase #5	$54.46	9.611%	$59.6942	$59.69	$59.70	$59.70
Purchase #6	$46.81	7.809%	$50.4654	$50.47	$50.45	$50.50
Purchase #7	$37.47	12.521%	$42.1616	$42.16	$42.15	$42.20
7 purchase totals =	$647.70		$702.8507	$702.86	$702.85	$702.80