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	$40.43	7.504%	$43.4639	$43.46	$43.45	$43.50
Purchase #2	$114.31	6.413%	$121.6407	$121.64	$121.65	$121.60
Purchase #3	$20.29	6.589%	$21.6269	$21.63	$21.65	$21.60
Purchase #4	$57.37	4.306%	$59.8404	$59.84	$59.85	$59.80
Purchase #5	$78.29	13.193%	$88.6188	$88.62	$88.60	$88.60
Purchase #6	$178.94	9.287%	$195.5582	$195.56	$195.55	$195.60
Purchase #7	$203.94	12.468%	$229.3672	$229.37	$229.35	$229.40
7 purchase totals =	$693.57		$760.1161	$760.12	$760.10	$760.10