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	$161.57	10.260%	$178.1471	$178.15	$178.15	$178.10
Purchase #2	$199.37	8.576%	$216.468	$216.47	$216.45	$216.50
Purchase #3	$149.40	6.139%	$158.5717	$158.57	$158.55	$158.60
Purchase #4	$132.35	8.408%	$143.478	$143.48	$143.50	$143.50
Purchase #5	$11.54	12.661%	$13.0011	$13.00	$13.00	$13.00
Purchase #6	$220.34	13.350%	$249.7554	$249.76	$249.75	$249.80
Purchase #7	$41.78	8.668%	$45.4015	$45.40	$45.40	$45.40
7 purchase totals =	$916.35		$1,004.8228	$1,004.83	$1,004.80	$1,004.90