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	$209.76	7.119%	$224.6928	$224.69	$224.70	$224.70
Purchase #2	$183.86	4.169%	$191.5251	$191.53	$191.55	$191.50
Purchase #3	$243.84	12.596%	$274.5541	$274.55	$274.55	$274.60
Purchase #4	$52.44	12.672%	$59.0852	$59.09	$59.10	$59.10
Purchase #5	$229.48	11.700%	$256.3292	$256.33	$256.35	$256.30
Purchase #6	$246.35	6.555%	$262.4982	$262.50	$262.50	$262.50
Purchase #7	$234.78	11.321%	$261.3594	$261.36	$261.35	$261.40
7 purchase totals =	$1,400.51		$1,530.0440	$1,530.05	$1,530.10	$1,530.10