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	$105.60	3.833%	$109.6476	$109.65	$109.65	$109.60
Purchase #2	$108.72	7.381%	$116.7446	$116.74	$116.75	$116.70
Purchase #3	$73.82	13.461%	$83.7569	$83.76	$83.75	$83.80
Purchase #4	$59.76	3.437%	$61.814	$61.81	$61.80	$61.80
Purchase #5	$25.51	13.153%	$28.8653	$28.87	$28.85	$28.90
Purchase #6	$26.61	4.784%	$27.883	$27.88	$27.90	$27.90
Purchase #7	$245.57	13.344%	$278.3389	$278.34	$278.35	$278.30
7 purchase totals =	$645.59		$707.0503	$707.05	$707.05	$707.00