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	$59.68	10.276%	$65.8127	$65.81	$65.80	$65.80
Purchase #2	$152.71	8.317%	$165.4109	$165.41	$165.40	$165.40
Purchase #3	$37.76	13.635%	$42.9086	$42.91	$42.90	$42.90
Purchase #4	$205.72	5.216%	$216.4504	$216.45	$216.45	$216.50
Purchase #5	$247.97	4.843%	$259.9792	$259.98	$260.00	$260.00
Purchase #6	$10.61	9.556%	$11.6239	$11.62	$11.60	$11.60
Purchase #7	$139.74	8.350%	$151.4083	$151.41	$151.40	$151.40
7 purchase totals =	$854.19		$913.5940	$913.59	$913.55	$913.60