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	$73.94	3.471%	$76.5065	$76.51	$76.50	$76.50
Purchase #2	$61.85	12.248%	$69.4254	$69.43	$69.45	$69.40
Purchase #3	$40.84	12.136%	$45.7963	$45.80	$45.80	$45.80
Purchase #4	$55.98	6.629%	$59.6909	$59.69	$59.70	$59.70
Purchase #5	$244.33	7.785%	$263.3511	$263.35	$263.35	$263.40
Purchase #6	$113.33	4.212%	$118.1035	$118.10	$118.10	$118.10
Purchase #7	$200.78	7.847%	$216.5352	$216.54	$216.55	$216.50
7 purchase totals =	$791.05		$849.4089	$849.42	$849.45	$849.40