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	$228.90	11.550%	$255.338	$255.34	$255.35	$255.30
Purchase #2	$54.91	12.134%	$61.5728	$61.57	$61.55	$61.60
Purchase #3	$103.53	5.776%	$109.5099	$109.51	$109.50	$109.50
Purchase #4	$181.47	12.209%	$203.6257	$203.63	$203.65	$203.60
Purchase #5	$172.82	13.654%	$196.4168	$196.42	$196.40	$196.40
Purchase #6	$198.35	5.712%	$209.6798	$209.68	$209.70	$209.70
Purchase #7	$157.72	4.405%	$164.6676	$164.67	$164.65	$164.70
7 purchase totals =	$1,097.70		$1,200.8106	$1,200.82	$1,200.80	$1,200.80