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	$67.70	10.751%	$74.9784	$74.98	$75.00	$75.00
Purchase #2	$161.56	6.216%	$171.6026	$171.60	$171.60	$171.60
Purchase #3	$97.98	13.722%	$111.4248	$111.42	$111.40	$111.40
Purchase #4	$118.35	11.360%	$131.7946	$131.79	$131.80	$131.80
Purchase #5	$151.29	11.386%	$168.5159	$168.52	$168.50	$168.50
Purchase #6	$132.84	10.502%	$146.7909	$146.79	$146.80	$146.80
Purchase #7	$91.42	10.379%	$100.9085	$100.91	$100.90	$100.90
7 purchase totals =	$821.14		$906.0157	$906.01	$906.00	$906.00