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	$52.59	6.229%	$55.8658	$55.87	$55.85	$55.90
Purchase #2	$63.40	13.776%	$72.134	$72.13	$72.15	$72.10
Purchase #3	$27.53	10.452%	$30.4074	$30.41	$30.40	$30.40
Purchase #4	$241.41	11.126%	$268.2693	$268.27	$268.25	$268.30
Purchase #5	$19.80	7.303%	$21.246	$21.25	$21.25	$21.20
Purchase #6	$215.73	6.739%	$230.268	$230.27	$230.25	$230.30
Purchase #7	$172.78	10.760%	$191.3711	$191.37	$191.35	$191.40
7 purchase totals =	$793.24		$869.5616	$869.57	$869.50	$869.60