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	$230.71	7.385%	$247.7479	$247.75	$247.75	$247.70
Purchase #2	$80.78	7.116%	$86.5283	$86.53	$86.55	$86.50
Purchase #3	$107.93	3.304%	$111.496	$111.50	$111.50	$111.50
Purchase #4	$116.75	12.816%	$131.7127	$131.71	$131.70	$131.70
Purchase #5	$149.55	5.310%	$157.4911	$157.49	$157.50	$157.50
Purchase #6	$179.71	4.236%	$187.3225	$187.32	$187.30	$187.30
Purchase #7	$108.30	9.390%	$118.4694	$118.47	$118.45	$118.50
7 purchase totals =	$973.73		$1,040.7679	$1,040.77	$1,040.75	$1,040.70