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	$158.66	8.574%	$172.2635	$172.26	$172.25	$172.30
Purchase #2	$225.57	6.755%	$240.8073	$240.81	$240.80	$240.80
Purchase #3	$39.47	9.747%	$43.3171	$43.32	$43.30	$43.30
Purchase #4	$143.92	3.329%	$148.7111	$148.71	$148.70	$148.70
Purchase #5	$170.46	8.729%	$185.3395	$185.34	$185.35	$185.30
Purchase #6	$225.54	3.575%	$233.6031	$233.60	$233.60	$233.60
Purchase #7	$68.70	5.401%	$72.4105	$72.41	$72.40	$72.40
7 purchase totals =	$1,032.32		$1,096.4521	$1,096.45	$1,096.40	$1,096.40