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	$43.36	11.619%	$48.398	$48.40	$48.40	$48.40
Purchase #2	$85.96	3.663%	$89.1087	$89.11	$89.10	$89.10
Purchase #3	$136.91	12.219%	$153.639	$153.64	$153.65	$153.60
Purchase #4	$200.43	13.544%	$227.5762	$227.58	$227.60	$227.60
Purchase #5	$149.37	11.439%	$166.4564	$166.46	$166.45	$166.50
Purchase #6	$121.60	7.315%	$130.495	$130.50	$130.50	$130.50
Purchase #7	$136.99	4.495%	$143.1477	$143.15	$143.15	$143.10
7 purchase totals =	$874.62		$958.8210	$958.84	$958.85	$958.80