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	$142.50	5.394%	$150.1865	$150.19	$150.20	$150.20
Purchase #2	$180.59	5.433%	$190.4015	$190.40	$190.40	$190.40
Purchase #3	$77.82	11.300%	$86.6137	$86.61	$86.60	$86.60
Purchase #4	$171.37	11.469%	$191.0244	$191.02	$191.00	$191.00
Purchase #5	$197.69	12.683%	$222.763	$222.76	$222.75	$222.80
Purchase #6	$96.66	12.551%	$108.7918	$108.79	$108.80	$108.80
Purchase #7	$5.70	3.576%	$5.9038	$5.90	$5.90	$5.90
7 purchase totals =	$872.33		$955.6847	$955.67	$955.65	$955.70