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	$97.48	6.734%	$104.0443	$104.04	$104.05	$104.00
Purchase #2	$200.32	8.219%	$216.7843	$216.78	$216.80	$216.80
Purchase #3	$223.66	8.402%	$242.4519	$242.45	$242.45	$242.50
Purchase #4	$184.25	3.187%	$190.122	$190.12	$190.10	$190.10
Purchase #5	$71.63	10.133%	$78.8883	$78.89	$78.90	$78.90
Purchase #6	$228.88	11.850%	$256.0023	$256.00	$256.00	$256.00
Purchase #7	$32.29	8.743%	$35.1131	$35.11	$35.10	$35.10
7 purchase totals =	$1,038.51		$1,123.4062	$1,123.39	$1,123.40	$1,123.40