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	$223.77	6.723%	$238.8141	$238.81	$238.80	$238.80
Purchase #2	$91.71	12.871%	$103.514	$103.51	$103.50	$103.50
Purchase #3	$218.27	12.531%	$245.6214	$245.62	$245.60	$245.60
Purchase #4	$9.67	8.355%	$10.4779	$10.48	$10.50	$10.50
Purchase #5	$243.29	12.745%	$274.2973	$274.30	$274.30	$274.30
Purchase #6	$245.38	7.123%	$262.8584	$262.86	$262.85	$262.90
Purchase #7	$50.31	12.816%	$56.7577	$56.76	$56.75	$56.80
7 purchase totals =	$1,082.40		$1,192.3408	$1,192.34	$1,192.30	$1,192.40