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	$137.39	11.559%	$153.2709	$153.27	$153.25	$153.30
Purchase #2	$97.54	3.492%	$100.9461	$100.95	$100.95	$100.90
Purchase #3	$232.57	9.152%	$253.8548	$253.85	$253.85	$253.90
Purchase #4	$59.57	13.339%	$67.516	$67.52	$67.50	$67.50
Purchase #5	$131.77	4.132%	$137.2147	$137.21	$137.20	$137.20
Purchase #6	$21.38	7.512%	$22.9861	$22.99	$23.00	$23.00
Purchase #7	$118.89	4.568%	$124.3209	$124.32	$124.30	$124.30
7 purchase totals =	$799.11		$860.1095	$860.11	$860.05	$860.10