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	$118.65	9.643%	$130.0914	$130.09	$130.10	$130.10
Purchase #2	$30.26	11.228%	$33.6576	$33.66	$33.65	$33.70
Purchase #3	$199.66	11.428%	$222.4771	$222.48	$222.50	$222.50
Purchase #4	$164.60	12.496%	$185.1684	$185.17	$185.15	$185.20
Purchase #5	$131.56	4.581%	$137.5868	$137.59	$137.60	$137.60
Purchase #6	$89.62	13.736%	$101.9302	$101.93	$101.95	$101.90
Purchase #7	$201.44	11.422%	$224.4485	$224.45	$224.45	$224.40
7 purchase totals =	$935.79		$1,035.3600	$1,035.37	$1,035.40	$1,035.40