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	$102.61	8.675%	$111.5114	$111.51	$111.50	$111.50
Purchase #2	$89.59	11.792%	$100.1545	$100.15	$100.15	$100.20
Purchase #3	$43.49	4.373%	$45.3918	$45.39	$45.40	$45.40
Purchase #4	$5.78	13.847%	$6.5804	$6.58	$6.60	$6.60
Purchase #5	$206.71	7.353%	$221.9094	$221.91	$221.90	$221.90
Purchase #6	$78.33	6.341%	$83.2969	$83.30	$83.30	$83.30
Purchase #7	$242.68	6.260%	$257.8718	$257.87	$257.85	$257.90
7 purchase totals =	$769.19		$826.7162	$826.71	$826.70	$826.80