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	$141.72	6.607%	$151.0834	$151.08	$151.10	$151.10
Purchase #2	$40.42	4.210%	$42.1217	$42.12	$42.10	$42.10
Purchase #3	$88.75	9.334%	$97.0339	$97.03	$97.05	$97.00
Purchase #4	$163.90	3.169%	$169.094	$169.09	$169.10	$169.10
Purchase #5	$135.60	3.539%	$140.3989	$140.40	$140.40	$140.40
Purchase #6	$71.64	11.110%	$79.5992	$79.60	$79.60	$79.60
Purchase #7	$57.82	5.773%	$61.1579	$61.16	$61.15	$61.20
7 purchase totals =	$699.85		$740.4890	$740.48	$740.50	$740.50