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	$189.79	4.333%	$198.0136	$198.01	$198.00	$198.00
Purchase #2	$239.71	10.401%	$264.6422	$264.64	$264.65	$264.60
Purchase #3	$120.77	9.845%	$132.6598	$132.66	$132.65	$132.70
Purchase #4	$26.58	7.518%	$28.5783	$28.58	$28.60	$28.60
Purchase #5	$214.91	3.113%	$221.6001	$221.60	$221.60	$221.60
Purchase #6	$32.59	3.235%	$33.6443	$33.64	$33.65	$33.60
Purchase #7	$222.81	9.775%	$244.5897	$244.59	$244.60	$244.60
7 purchase totals =	$1,047.16		$1,123.7280	$1,123.72	$1,123.75	$1,123.70