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	$74.86	11.137%	$83.1972	$83.20	$83.20	$83.20
Purchase #2	$57.60	5.352%	$60.6828	$60.68	$60.70	$60.70
Purchase #3	$108.78	3.498%	$112.5851	$112.59	$112.60	$112.60
Purchase #4	$206.35	7.544%	$221.917	$221.92	$221.90	$221.90
Purchase #5	$86.75	4.148%	$90.3484	$90.35	$90.35	$90.30
Purchase #6	$39.69	8.143%	$42.922	$42.92	$42.90	$42.90
Purchase #7	$170.67	6.725%	$182.1476	$182.15	$182.15	$182.10
7 purchase totals =	$744.70		$793.8001	$793.81	$793.80	$793.70