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	$176.39	8.623%	$191.6001	$191.60	$191.60	$191.60
Purchase #2	$129.74	9.286%	$141.7877	$141.79	$141.80	$141.80
Purchase #3	$12.71	7.458%	$13.6579	$13.66	$13.65	$13.70
Purchase #4	$59.68	3.658%	$61.8631	$61.86	$61.85	$61.90
Purchase #5	$90.71	11.718%	$101.3394	$101.34	$101.35	$101.30
Purchase #6	$147.60	12.780%	$166.4633	$166.46	$166.45	$166.50
Purchase #7	$182.89	11.802%	$204.4747	$204.47	$204.45	$204.50
7 purchase totals =	$799.72		$881.1862	$881.18	$881.15	$881.30