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	$200.50	12.682%	$225.9274	$225.93	$225.95	$225.90
Purchase #2	$158.94	12.706%	$179.1349	$179.13	$179.15	$179.10
Purchase #3	$12.91	3.157%	$13.3176	$13.32	$13.30	$13.30
Purchase #4	$71.57	8.739%	$77.8245	$77.82	$77.80	$77.80
Purchase #5	$97.30	12.646%	$109.6046	$109.60	$109.60	$109.60
Purchase #6	$33.68	10.596%	$37.2487	$37.25	$37.25	$37.20
Purchase #7	$219.42	11.119%	$243.8173	$243.82	$243.80	$243.80
7 purchase totals =	$794.32		$886.8750	$886.87	$886.85	$886.70