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	$32.76	4.120%	$34.1097	$34.11	$34.10	$34.10
Purchase #2	$82.86	7.364%	$88.9618	$88.96	$88.95	$89.00
Purchase #3	$144.58	11.450%	$161.1344	$161.13	$161.15	$161.10
Purchase #4	$110.27	3.171%	$113.7667	$113.77	$113.75	$113.80
Purchase #5	$50.51	8.700%	$54.9044	$54.90	$54.90	$54.90
Purchase #6	$82.61	8.857%	$89.9268	$89.93	$89.95	$89.90
Purchase #7	$237.59	7.572%	$255.5803	$255.58	$255.60	$255.60
7 purchase totals =	$741.18		$798.3841	$798.38	$798.40	$798.40