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	$128.92	13.664%	$146.5356	$146.54	$146.55	$146.50
Purchase #2	$174.86	9.364%	$191.2339	$191.23	$191.25	$191.20
Purchase #3	$8.38	6.509%	$8.9255	$8.93	$8.95	$8.90
Purchase #4	$132.83	11.377%	$147.9421	$147.94	$147.95	$147.90
Purchase #5	$194.63	11.612%	$217.2304	$217.23	$217.25	$217.20
Purchase #6	$185.56	12.518%	$208.7884	$208.79	$208.80	$208.80
Purchase #7	$139.70	3.201%	$144.1718	$144.17	$144.15	$144.20
7 purchase totals =	$964.88		$1,064.8277	$1,064.83	$1,064.90	$1,064.70