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	$201.84	3.781%	$209.4716	$209.47	$209.45	$209.50
Purchase #2	$168.93	13.433%	$191.6224	$191.62	$191.60	$191.60
Purchase #3	$159.39	8.282%	$172.5907	$172.59	$172.60	$172.60
Purchase #4	$199.28	6.517%	$212.2671	$212.27	$212.25	$212.30
Purchase #5	$102.28	9.396%	$111.8902	$111.89	$111.90	$111.90
Purchase #6	$185.81	7.150%	$199.0954	$199.10	$199.10	$199.10
Purchase #7	$106.71	12.549%	$120.101	$120.10	$120.10	$120.10
7 purchase totals =	$1,124.24		$1,217.0384	$1,217.04	$1,217.00	$1,217.10