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	$105.66	8.675%	$114.826	$114.83	$114.85	$114.80
Purchase #2	$21.72	7.606%	$23.372	$23.37	$23.35	$23.40
Purchase #3	$111.33	12.224%	$124.939	$124.94	$124.95	$124.90
Purchase #4	$6.70	6.438%	$7.1313	$7.13	$7.15	$7.10
Purchase #5	$7.30	4.250%	$7.6103	$7.61	$7.60	$7.60
Purchase #6	$58.36	11.788%	$65.2395	$65.24	$65.25	$65.20
Purchase #7	$74.33	5.426%	$78.3631	$78.36	$78.35	$78.40
7 purchase totals =	$385.40		$421.4812	$421.48	$421.50	$421.40