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	$104.53	6.187%	$110.9973	$111.00	$111.00	$111.00
Purchase #2	$36.29	11.595%	$40.4978	$40.50	$40.50	$40.50
Purchase #3	$89.84	3.845%	$93.2943	$93.29	$93.30	$93.30
Purchase #4	$206.42	7.175%	$221.2306	$221.23	$221.25	$221.20
Purchase #5	$69.25	10.362%	$76.4257	$76.43	$76.45	$76.40
Purchase #6	$39.67	6.562%	$42.2731	$42.27	$42.25	$42.30
Purchase #7	$164.76	4.353%	$171.932	$171.93	$171.95	$171.90
7 purchase totals =	$710.76		$756.6508	$756.65	$756.70	$756.60