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	$28.39	3.573%	$29.4044	$29.40	$29.40	$29.40
Purchase #2	$78.69	12.445%	$88.483	$88.48	$88.50	$88.50
Purchase #3	$229.32	9.308%	$250.6651	$250.67	$250.65	$250.70
Purchase #4	$235.45	5.530%	$248.4704	$248.47	$248.45	$248.50
Purchase #5	$146.25	12.263%	$164.1846	$164.18	$164.20	$164.20
Purchase #6	$213.51	3.739%	$221.4931	$221.49	$221.50	$221.50
Purchase #7	$229.42	10.598%	$253.7339	$253.73	$253.75	$253.70
7 purchase totals =	$1,161.03		$1,256.4345	$1,256.42	$1,256.45	$1,256.50