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	$179.39	8.732%	$195.0543	$195.05	$195.05	$195.10
Purchase #2	$6.51	7.759%	$7.0151	$7.02	$7.00	$7.00
Purchase #3	$21.81	10.234%	$24.042	$24.04	$24.05	$24.00
Purchase #4	$121.37	13.700%	$137.9977	$138.00	$138.00	$138.00
Purchase #5	$82.59	8.523%	$89.6291	$89.63	$89.65	$89.60
Purchase #6	$40.58	12.123%	$45.4995	$45.50	$45.50	$45.50
Purchase #7	$169.72	11.168%	$188.6743	$188.67	$188.65	$188.70
7 purchase totals =	$621.97		$687.9120	$687.91	$687.90	$687.90