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	$121.62	8.107%	$131.4797	$131.48	$131.50	$131.50
Purchase #2	$134.46	13.764%	$152.9671	$152.97	$152.95	$153.00
Purchase #3	$180.77	5.118%	$190.0218	$190.02	$190.00	$190.00
Purchase #4	$67.88	8.557%	$73.6885	$73.69	$73.70	$73.70
Purchase #5	$110.88	4.823%	$116.2277	$116.23	$116.25	$116.20
Purchase #6	$146.78	8.384%	$159.086	$159.09	$159.10	$159.10
Purchase #7	$137.59	8.250%	$148.9412	$148.94	$148.95	$148.90
7 purchase totals =	$899.98		$972.4120	$972.42	$972.45	$972.40