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	$97.82	3.820%	$101.5567	$101.56	$101.55	$101.60
Purchase #2	$72.51	5.594%	$76.5662	$76.57	$76.55	$76.60
Purchase #3	$153.33	12.376%	$172.3061	$172.31	$172.30	$172.30
Purchase #4	$187.70	6.410%	$199.7316	$199.73	$199.75	$199.70
Purchase #5	$69.67	12.422%	$78.3244	$78.32	$78.30	$78.30
Purchase #6	$155.77	13.834%	$177.3192	$177.32	$177.30	$177.30
Purchase #7	$6.90	8.856%	$7.5111	$7.51	$7.50	$7.50
7 purchase totals =	$743.70		$813.3153	$813.32	$813.25	$813.30