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	$156.37	10.197%	$172.315	$172.32	$172.30	$172.30
Purchase #2	$76.63	8.726%	$83.3167	$83.32	$83.30	$83.30
Purchase #3	$82.26	13.146%	$93.0739	$93.07	$93.05	$93.10
Purchase #4	$115.82	10.730%	$128.2475	$128.25	$128.25	$128.20
Purchase #5	$52.47	10.315%	$57.8823	$57.88	$57.90	$57.90
Purchase #6	$145.57	11.676%	$162.5668	$162.57	$162.55	$162.60
Purchase #7	$187.86	6.560%	$200.1836	$200.18	$200.20	$200.20
7 purchase totals =	$816.98		$897.5858	$897.59	$897.55	$897.60