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	$74.34	5.535%	$78.4547	$78.45	$78.45	$78.50
Purchase #2	$169.79	12.289%	$190.6555	$190.66	$190.65	$190.70
Purchase #3	$247.81	7.649%	$266.765	$266.77	$266.75	$266.80
Purchase #4	$185.94	5.683%	$196.507	$196.51	$196.50	$196.50
Purchase #5	$192.71	5.285%	$202.8947	$202.89	$202.90	$202.90
Purchase #6	$119.69	6.236%	$127.1539	$127.15	$127.15	$127.20
Purchase #7	$186.78	8.208%	$202.1109	$202.11	$202.10	$202.10
7 purchase totals =	$1,177.06		$1,264.5417	$1,264.54	$1,264.50	$1,264.70