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	$246.64	4.142%	$256.8558	$256.86	$256.85	$256.90
Purchase #2	$203.26	9.292%	$222.1469	$222.15	$222.15	$222.10
Purchase #3	$224.31	12.809%	$253.0419	$253.04	$253.05	$253.00
Purchase #4	$43.52	11.181%	$48.386	$48.39	$48.40	$48.40
Purchase #5	$18.99	11.281%	$21.1323	$21.13	$21.15	$21.10
Purchase #6	$238.46	8.623%	$259.0224	$259.02	$259.00	$259.00
Purchase #7	$42.96	3.722%	$44.559	$44.56	$44.55	$44.60
7 purchase totals =	$1,018.14		$1,105.1443	$1,105.15	$1,105.15	$1,105.10