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	$70.37	5.534%	$74.2643	$74.26	$74.25	$74.30
Purchase #2	$147.76	8.203%	$159.8808	$159.88	$159.90	$159.90
Purchase #3	$171.71	12.740%	$193.5859	$193.59	$193.60	$193.60
Purchase #4	$163.78	13.417%	$185.7544	$185.75	$185.75	$185.80
Purchase #5	$120.34	9.763%	$132.0888	$132.09	$132.10	$132.10
Purchase #6	$152.40	6.628%	$162.5011	$162.50	$162.50	$162.50
Purchase #7	$137.70	11.391%	$153.3854	$153.39	$153.40	$153.40
7 purchase totals =	$964.06		$1,061.4607	$1,061.46	$1,061.50	$1,061.60