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	$103.73	7.151%	$111.1477	$111.15	$111.15	$111.10
Purchase #2	$80.83	12.788%	$91.1665	$91.17	$91.15	$91.20
Purchase #3	$49.82	8.688%	$54.1484	$54.15	$54.15	$54.10
Purchase #4	$203.85	11.818%	$227.941	$227.94	$227.95	$227.90
Purchase #5	$123.57	3.234%	$127.5663	$127.57	$127.55	$127.60
Purchase #6	$10.47	3.648%	$10.8519	$10.85	$10.85	$10.90
Purchase #7	$244.86	6.467%	$260.6951	$260.70	$260.70	$260.70
7 purchase totals =	$817.13		$883.5169	$883.53	$883.50	$883.50