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	$219.90	12.633%	$247.68	$247.68	$247.70	$247.70
Purchase #2	$240.28	6.221%	$255.2278	$255.23	$255.25	$255.20
Purchase #3	$61.60	9.774%	$67.6208	$67.62	$67.60	$67.60
Purchase #4	$118.75	6.872%	$126.9105	$126.91	$126.90	$126.90
Purchase #5	$26.53	4.124%	$27.6241	$27.62	$27.60	$27.60
Purchase #6	$203.88	10.221%	$224.7186	$224.72	$224.70	$224.70
Purchase #7	$50.88	6.561%	$54.2182	$54.22	$54.20	$54.20
7 purchase totals =	$921.82		$1,004.0000	$1,004.00	$1,003.95	$1,003.90