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	$172.48	11.358%	$192.0703	$192.07	$192.05	$192.10
Purchase #2	$113.61	10.810%	$125.8912	$125.89	$125.90	$125.90
Purchase #3	$86.89	6.404%	$92.4544	$92.45	$92.45	$92.50
Purchase #4	$39.61	6.481%	$42.1771	$42.18	$42.20	$42.20
Purchase #5	$75.47	6.215%	$80.1605	$80.16	$80.15	$80.20
Purchase #6	$54.88	6.832%	$58.6294	$58.63	$58.65	$58.60
Purchase #7	$80.34	3.773%	$83.3712	$83.37	$83.35	$83.40
7 purchase totals =	$623.28		$674.7541	$674.75	$674.75	$674.90