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	$176.72	3.391%	$182.7126	$182.71	$182.70	$182.70
Purchase #2	$132.25	13.300%	$149.8393	$149.84	$149.85	$149.80
Purchase #3	$12.58	12.190%	$14.1135	$14.11	$14.10	$14.10
Purchase #4	$72.65	13.798%	$82.6742	$82.67	$82.65	$82.70
Purchase #5	$202.71	9.831%	$222.6384	$222.64	$222.65	$222.60
Purchase #6	$98.89	7.725%	$106.5293	$106.53	$106.55	$106.50
Purchase #7	$33.87	10.700%	$37.4941	$37.49	$37.50	$37.50
7 purchase totals =	$729.67		$796.0014	$795.99	$796.00	$795.90