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	$70.31	11.208%	$78.1903	$78.19	$78.20	$78.20
Purchase #2	$232.42	5.402%	$244.9753	$244.98	$245.00	$245.00
Purchase #3	$245.67	8.233%	$265.896	$265.90	$265.90	$265.90
Purchase #4	$86.81	5.124%	$91.2581	$91.26	$91.25	$91.30
Purchase #5	$219.89	11.823%	$245.8876	$245.89	$245.90	$245.90
Purchase #6	$235.32	12.779%	$265.3915	$265.39	$265.40	$265.40
Purchase #7	$220.42	12.464%	$247.8931	$247.89	$247.90	$247.90
7 purchase totals =	$1,310.84		$1,439.4919	$1,439.50	$1,439.55	$1,439.60