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	$11.67	12.373%	$13.1139	$13.11	$13.10	$13.10
Purchase #2	$98.47	8.548%	$106.8872	$106.89	$106.90	$106.90
Purchase #3	$35.34	10.160%	$38.9305	$38.93	$38.95	$38.90
Purchase #4	$92.40	11.744%	$103.2515	$103.25	$103.25	$103.30
Purchase #5	$83.99	8.229%	$90.9015	$90.90	$90.90	$90.90
Purchase #6	$186.27	4.341%	$194.356	$194.36	$194.35	$194.40
Purchase #7	$175.38	13.665%	$199.3457	$199.35	$199.35	$199.30
7 purchase totals =	$683.52		$746.7863	$746.79	$746.80	$746.80