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	$230.28	10.319%	$254.0426	$254.04	$254.05	$254.00
Purchase #2	$66.25	10.285%	$73.0638	$73.06	$73.05	$73.10
Purchase #3	$242.67	12.449%	$272.88	$272.88	$272.90	$272.90
Purchase #4	$199.39	4.663%	$208.6876	$208.69	$208.70	$208.70
Purchase #5	$23.53	5.659%	$24.8616	$24.86	$24.85	$24.90
Purchase #6	$80.58	6.130%	$85.5196	$85.52	$85.50	$85.50
Purchase #7	$174.64	3.662%	$181.0353	$181.04	$181.05	$181.00
7 purchase totals =	$1,017.34		$1,100.0905	$1,100.09	$1,100.10	$1,100.10