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	$111.56	6.617%	$118.9419	$118.94	$118.95	$118.90
Purchase #2	$74.37	11.866%	$83.1947	$83.19	$83.20	$83.20
Purchase #3	$110.63	5.781%	$117.0255	$117.03	$117.05	$117.00
Purchase #4	$65.49	10.405%	$72.3042	$72.30	$72.30	$72.30
Purchase #5	$69.48	9.239%	$75.8993	$75.90	$75.90	$75.90
Purchase #6	$128.76	13.325%	$145.9173	$145.92	$145.90	$145.90
Purchase #7	$136.81	10.272%	$150.8631	$150.86	$150.85	$150.90
7 purchase totals =	$697.10		$764.1460	$764.14	$764.15	$764.10