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	$124.45	10.507%	$137.526	$137.53	$137.55	$137.50
Purchase #2	$231.73	6.595%	$247.0126	$247.01	$247.00	$247.00
Purchase #3	$56.57	11.394%	$63.0156	$63.02	$63.00	$63.00
Purchase #4	$103.48	7.386%	$111.123	$111.12	$111.10	$111.10
Purchase #5	$169.52	12.107%	$190.0438	$190.04	$190.05	$190.00
Purchase #6	$145.89	5.543%	$153.9767	$153.98	$154.00	$154.00
Purchase #7	$52.32	12.367%	$58.7904	$58.79	$58.80	$58.80
7 purchase totals =	$883.96		$961.4881	$961.49	$961.50	$961.40