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	$71.98	4.132%	$74.9542	$74.95	$74.95	$75.00
Purchase #2	$12.90	6.345%	$13.7185	$13.72	$13.70	$13.70
Purchase #3	$178.40	13.758%	$202.9443	$202.94	$202.95	$202.90
Purchase #4	$36.30	11.599%	$40.5104	$40.51	$40.50	$40.50
Purchase #5	$61.56	6.429%	$65.5177	$65.52	$65.50	$65.50
Purchase #6	$136.94	9.346%	$149.7384	$149.74	$149.75	$149.70
Purchase #7	$111.78	6.362%	$118.8914	$118.89	$118.90	$118.90
7 purchase totals =	$609.86		$666.2749	$666.27	$666.25	$666.20