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	$224.26	8.109%	$242.4452	$242.45	$242.45	$242.40
Purchase #2	$173.39	6.209%	$184.1558	$184.16	$184.15	$184.20
Purchase #3	$99.33	12.727%	$111.9717	$111.97	$111.95	$112.00
Purchase #4	$242.79	13.442%	$275.4258	$275.43	$275.45	$275.40
Purchase #5	$79.54	3.263%	$82.1354	$82.14	$82.15	$82.10
Purchase #6	$48.56	6.182%	$51.562	$51.56	$51.55	$51.60
Purchase #7	$169.93	12.722%	$191.5485	$191.55	$191.55	$191.50
7 purchase totals =	$1,037.80		$1,139.2444	$1,139.26	$1,139.25	$1,139.20