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	$165.30	5.190%	$173.8791	$173.88	$173.90	$173.90
Purchase #2	$204.97	4.110%	$213.3943	$213.39	$213.40	$213.40
Purchase #3	$56.81	6.380%	$60.4345	$60.43	$60.45	$60.40
Purchase #4	$146.90	12.591%	$165.3962	$165.40	$165.40	$165.40
Purchase #5	$127.78	10.283%	$140.9196	$140.92	$140.90	$140.90
Purchase #6	$196.86	10.141%	$216.8236	$216.82	$216.80	$216.80
Purchase #7	$146.57	6.853%	$156.6144	$156.61	$156.60	$156.60
7 purchase totals =	$1,045.19		$1,127.4617	$1,127.45	$1,127.45	$1,127.40