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	$131.76	10.816%	$146.0112	$146.01	$146.00	$146.00
Purchase #2	$30.72	9.213%	$33.5502	$33.55	$33.55	$33.60
Purchase #3	$203.92	8.417%	$221.0839	$221.08	$221.10	$221.10
Purchase #4	$107.97	10.426%	$119.227	$119.23	$119.25	$119.20
Purchase #5	$40.28	6.391%	$42.8543	$42.85	$42.85	$42.90
Purchase #6	$215.28	13.278%	$243.8649	$243.86	$243.85	$243.90
Purchase #7	$16.90	9.135%	$18.4438	$18.44	$18.45	$18.40
7 purchase totals =	$746.83		$825.0353	$825.02	$825.05	$825.10