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	$54.37	8.129%	$58.7897	$58.79	$58.80	$58.80
Purchase #2	$30.37	10.384%	$33.5236	$33.52	$33.50	$33.50
Purchase #3	$25.68	9.464%	$28.1104	$28.11	$28.10	$28.10
Purchase #4	$42.77	6.651%	$45.6146	$45.61	$45.60	$45.60
Purchase #5	$132.53	5.117%	$139.3116	$139.31	$139.30	$139.30
Purchase #6	$174.71	12.274%	$196.1539	$196.15	$196.15	$196.20
Purchase #7	$110.26	4.119%	$114.8016	$114.80	$114.80	$114.80
7 purchase totals =	$570.69		$616.3054	$616.29	$616.25	$616.30