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	$10.89	3.322%	$11.2518	$11.25	$11.25	$11.30
Purchase #2	$221.52	9.385%	$242.3097	$242.31	$242.30	$242.30
Purchase #3	$219.54	3.417%	$227.0417	$227.04	$227.05	$227.00
Purchase #4	$104.31	6.447%	$111.0349	$111.03	$111.05	$111.00
Purchase #5	$244.81	3.801%	$254.1152	$254.12	$254.10	$254.10
Purchase #6	$9.87	5.430%	$10.4059	$10.41	$10.40	$10.40
Purchase #7	$143.43	8.768%	$156.0059	$156.01	$156.00	$156.00
7 purchase totals =	$954.37		$1,012.1651	$1,012.17	$1,012.15	$1,012.10