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	$198.37	5.618%	$209.5144	$209.51	$209.50	$209.50
Purchase #2	$196.90	12.748%	$222.0008	$222.00	$222.00	$222.00
Purchase #3	$76.77	11.695%	$85.7483	$85.75	$85.75	$85.70
Purchase #4	$158.64	3.575%	$164.3114	$164.31	$164.30	$164.30
Purchase #5	$145.32	13.764%	$165.3218	$165.32	$165.30	$165.30
Purchase #6	$58.72	3.365%	$60.6959	$60.70	$60.70	$60.70
Purchase #7	$46.26	4.116%	$48.1641	$48.16	$48.15	$48.20
7 purchase totals =	$880.98		$955.7567	$955.75	$955.70	$955.70