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	$232.29	9.660%	$254.7292	$254.73	$254.75	$254.70
Purchase #2	$30.25	7.520%	$32.5248	$32.52	$32.50	$32.50
Purchase #3	$60.88	13.317%	$68.9874	$68.99	$69.00	$69.00
Purchase #4	$144.89	5.179%	$152.3939	$152.39	$152.40	$152.40
Purchase #5	$218.90	7.610%	$235.5583	$235.56	$235.55	$235.60
Purchase #6	$94.94	5.217%	$99.893	$99.89	$99.90	$99.90
Purchase #7	$28.69	11.746%	$32.0599	$32.06	$32.05	$32.10
7 purchase totals =	$810.84		$876.1465	$876.14	$876.15	$876.20