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	$65.43	3.862%	$67.9569	$67.96	$67.95	$68.00
Purchase #2	$145.73	7.764%	$157.0445	$157.04	$157.05	$157.00
Purchase #3	$36.99	13.563%	$42.007	$42.01	$42.00	$42.00
Purchase #4	$180.86	4.203%	$188.4615	$188.46	$188.45	$188.50
Purchase #5	$30.89	5.692%	$32.6483	$32.65	$32.65	$32.60
Purchase #6	$159.69	8.555%	$173.3515	$173.35	$173.35	$173.40
Purchase #7	$144.59	4.593%	$151.231	$151.23	$151.25	$151.20
7 purchase totals =	$764.18		$812.7007	$812.70	$812.70	$812.70