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	$216.48	4.107%	$225.3708	$225.37	$225.35	$225.40
Purchase #2	$203.31	6.667%	$216.8647	$216.86	$216.85	$216.90
Purchase #3	$119.70	4.225%	$124.7573	$124.76	$124.75	$124.80
Purchase #4	$29.29	13.480%	$33.2383	$33.24	$33.25	$33.20
Purchase #5	$137.28	5.104%	$144.2868	$144.29	$144.30	$144.30
Purchase #6	$146.32	3.867%	$151.9782	$151.98	$152.00	$152.00
Purchase #7	$61.36	6.446%	$65.3153	$65.32	$65.30	$65.30
7 purchase totals =	$913.74		$961.8114	$961.82	$961.80	$961.90