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	$105.95	5.472%	$111.7476	$111.75	$111.75	$111.70
Purchase #2	$237.38	13.630%	$269.7349	$269.73	$269.75	$269.70
Purchase #3	$151.70	3.734%	$157.3645	$157.36	$157.35	$157.40
Purchase #4	$112.39	10.478%	$124.1662	$124.17	$124.15	$124.20
Purchase #5	$215.47	12.429%	$242.2508	$242.25	$242.25	$242.30
Purchase #6	$14.92	5.142%	$15.6872	$15.69	$15.70	$15.70
Purchase #7	$89.53	11.465%	$99.7946	$99.79	$99.80	$99.80
7 purchase totals =	$927.34		$1,020.7458	$1,020.74	$1,020.75	$1,020.80