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	$146.41	10.681%	$162.0481	$162.05	$162.05	$162.00
Purchase #2	$27.39	6.480%	$29.1649	$29.16	$29.15	$29.20
Purchase #3	$54.86	4.769%	$57.4763	$57.48	$57.50	$57.50
Purchase #4	$210.37	10.581%	$232.6292	$232.63	$232.65	$232.60
Purchase #5	$65.45	12.182%	$73.4231	$73.42	$73.40	$73.40
Purchase #6	$137.38	6.485%	$146.2891	$146.29	$146.30	$146.30
Purchase #7	$82.74	8.645%	$89.8929	$89.89	$89.90	$89.90
7 purchase totals =	$724.60		$790.9236	$790.92	$790.95	$790.90