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	$72.88	13.565%	$82.7662	$82.77	$82.75	$82.80
Purchase #2	$50.99	11.409%	$56.8074	$56.81	$56.80	$56.80
Purchase #3	$242.48	7.500%	$260.666	$260.67	$260.65	$260.70
Purchase #4	$99.56	12.388%	$111.8935	$111.89	$111.90	$111.90
Purchase #5	$9.47	13.681%	$10.7656	$10.77	$10.75	$10.80
Purchase #6	$64.34	8.655%	$69.9086	$69.91	$69.90	$69.90
Purchase #7	$37.62	10.354%	$41.5152	$41.52	$41.50	$41.50
7 purchase totals =	$577.34		$634.3225	$634.34	$634.25	$634.40