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	$61.30	6.599%	$65.3452	$65.35	$65.35	$65.30
Purchase #2	$192.67	9.521%	$211.0141	$211.01	$211.00	$211.00
Purchase #3	$188.56	4.302%	$196.6719	$196.67	$196.65	$196.70
Purchase #4	$108.60	7.372%	$116.606	$116.61	$116.60	$116.60
Purchase #5	$108.78	13.816%	$123.809	$123.81	$123.80	$123.80
Purchase #6	$140.33	4.479%	$146.6154	$146.62	$146.60	$146.60
Purchase #7	$35.50	12.382%	$39.8956	$39.90	$39.90	$39.90
7 purchase totals =	$835.74		$899.9572	$899.97	$899.90	$899.90