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	$156.96	3.591%	$162.5964	$162.60	$162.60	$162.60
Purchase #2	$171.69	7.337%	$184.2869	$184.29	$184.30	$184.30
Purchase #3	$144.49	7.540%	$155.3845	$155.38	$155.40	$155.40
Purchase #4	$61.41	8.732%	$66.7723	$66.77	$66.75	$66.80
Purchase #5	$54.88	11.389%	$61.1303	$61.13	$61.15	$61.10
Purchase #6	$70.58	8.257%	$76.4078	$76.41	$76.40	$76.40
Purchase #7	$35.64	12.228%	$39.9981	$40.00	$40.00	$40.00
7 purchase totals =	$695.65		$746.5763	$746.58	$746.60	$746.60