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	$110.38	5.637%	$116.6021	$116.60	$116.60	$116.60
Purchase #2	$22.52	11.331%	$25.0717	$25.07	$25.05	$25.10
Purchase #3	$72.43	5.547%	$76.4477	$76.45	$76.45	$76.40
Purchase #4	$162.77	3.190%	$167.9624	$167.96	$167.95	$168.00
Purchase #5	$150.86	7.470%	$162.1292	$162.13	$162.15	$162.10
Purchase #6	$10.56	8.443%	$11.4516	$11.45	$11.45	$11.50
Purchase #7	$12.34	7.209%	$13.2296	$13.23	$13.25	$13.20
7 purchase totals =	$541.86		$572.8943	$572.89	$572.90	$572.90