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	$149.74	5.625%	$158.1629	$158.16	$158.15	$158.20
Purchase #2	$73.78	10.386%	$81.4428	$81.44	$81.45	$81.40
Purchase #3	$59.68	10.666%	$66.0455	$66.05	$66.05	$66.00
Purchase #4	$59.45	3.700%	$61.6497	$61.65	$61.65	$61.60
Purchase #5	$42.85	5.330%	$45.1339	$45.13	$45.15	$45.10
Purchase #6	$88.71	10.791%	$98.2827	$98.28	$98.30	$98.30
Purchase #7	$96.79	8.785%	$105.293	$105.29	$105.30	$105.30
7 purchase totals =	$571.00		$616.0105	$616.00	$616.05	$615.90