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	$32.57	11.541%	$36.3289	$36.33	$36.35	$36.30
Purchase #2	$147.52	4.321%	$153.8943	$153.89	$153.90	$153.90
Purchase #3	$155.42	4.460%	$162.3517	$162.35	$162.35	$162.40
Purchase #4	$175.96	9.510%	$192.6938	$192.69	$192.70	$192.70
Purchase #5	$37.42	13.263%	$42.383	$42.38	$42.40	$42.40
Purchase #6	$193.47	3.569%	$200.3749	$200.37	$200.35	$200.40
Purchase #7	$93.40	4.125%	$97.2528	$97.25	$97.25	$97.30
7 purchase totals =	$835.76		$885.2794	$885.26	$885.30	$885.40