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	$126.38	13.626%	$143.6005	$143.60	$143.60	$143.60
Purchase #2	$60.29	9.259%	$65.8723	$65.87	$65.85	$65.90
Purchase #3	$212.90	4.482%	$222.4422	$222.44	$222.45	$222.40
Purchase #4	$33.38	10.631%	$36.9286	$36.93	$36.95	$36.90
Purchase #5	$12.94	9.550%	$14.1758	$14.18	$14.20	$14.20
Purchase #6	$145.42	10.520%	$160.7182	$160.72	$160.70	$160.70
Purchase #7	$200.94	4.746%	$210.4766	$210.48	$210.50	$210.50
7 purchase totals =	$792.25		$854.2142	$854.22	$854.25	$854.20