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	$93.93	6.475%	$100.012	$100.01	$100.00	$100.00
Purchase #2	$24.72	11.389%	$27.5354	$27.54	$27.55	$27.50
Purchase #3	$190.81	4.377%	$199.1618	$199.16	$199.15	$199.20
Purchase #4	$188.88	9.239%	$206.3306	$206.33	$206.35	$206.30
Purchase #5	$199.48	8.610%	$216.6552	$216.66	$216.65	$216.70
Purchase #6	$79.82	10.627%	$88.3025	$88.30	$88.30	$88.30
Purchase #7	$173.97	6.739%	$185.6938	$185.69	$185.70	$185.70
7 purchase totals =	$951.61		$1,023.6913	$1,023.69	$1,023.70	$1,023.70