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	$100.56	4.618%	$105.2039	$105.20	$105.20	$105.20
Purchase #2	$174.34	10.355%	$192.3929	$192.39	$192.40	$192.40
Purchase #3	$44.83	4.569%	$46.8783	$46.88	$46.90	$46.90
Purchase #4	$222.25	5.454%	$234.3715	$234.37	$234.35	$234.40
Purchase #5	$172.78	4.480%	$180.5205	$180.52	$180.50	$180.50
Purchase #6	$236.43	4.454%	$246.9606	$246.96	$246.95	$247.00
Purchase #7	$42.90	6.507%	$45.6915	$45.69	$45.70	$45.70
7 purchase totals =	$994.09		$1,052.0192	$1,052.01	$1,052.00	$1,052.10