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	$42.72	5.362%	$45.0106	$45.01	$45.00	$45.00
Purchase #2	$250.57	8.499%	$271.8659	$271.87	$271.85	$271.90
Purchase #3	$111.69	10.562%	$123.4867	$123.49	$123.50	$123.50
Purchase #4	$244.37	3.740%	$253.5094	$253.51	$253.50	$253.50
Purchase #5	$228.41	8.214%	$247.1716	$247.17	$247.15	$247.20
Purchase #6	$207.61	7.195%	$222.5475	$222.55	$222.55	$222.50
Purchase #7	$206.73	7.479%	$222.1913	$222.19	$222.20	$222.20
7 purchase totals =	$1,292.10		$1,385.7830	$1,385.79	$1,385.75	$1,385.80