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	$137.76	9.531%	$150.8899	$150.89	$150.90	$150.90
Purchase #2	$185.29	13.578%	$210.4487	$210.45	$210.45	$210.40
Purchase #3	$6.69	5.243%	$7.0408	$7.04	$7.05	$7.00
Purchase #4	$146.49	10.826%	$162.349	$162.35	$162.35	$162.30
Purchase #5	$49.26	11.468%	$54.9091	$54.91	$54.90	$54.90
Purchase #6	$224.40	12.503%	$252.4567	$252.46	$252.45	$252.50
Purchase #7	$185.72	6.394%	$197.5949	$197.59	$197.60	$197.60
7 purchase totals =	$935.61		$1,035.6891	$1,035.69	$1,035.70	$1,035.60