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	$150.90	11.589%	$168.3878	$168.39	$168.40	$168.40
Purchase #2	$151.97	8.350%	$164.6595	$164.66	$164.65	$164.70
Purchase #3	$157.88	9.472%	$172.8344	$172.83	$172.85	$172.80
Purchase #4	$60.76	11.538%	$67.7705	$67.77	$67.75	$67.80
Purchase #5	$233.70	6.520%	$248.9372	$248.94	$248.95	$248.90
Purchase #6	$157.38	6.265%	$167.2399	$167.24	$167.25	$167.20
Purchase #7	$25.28	4.303%	$26.3678	$26.37	$26.35	$26.40
7 purchase totals =	$937.87		$1,016.1971	$1,016.20	$1,016.20	$1,016.20