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	$10.59	3.351%	$10.9449	$10.94	$10.95	$10.90
Purchase #2	$226.84	6.309%	$241.1513	$241.15	$241.15	$241.20
Purchase #3	$184.34	6.610%	$196.5249	$196.52	$196.50	$196.50
Purchase #4	$31.29	7.234%	$33.5535	$33.55	$33.55	$33.60
Purchase #5	$192.47	12.139%	$215.8339	$215.83	$215.85	$215.80
Purchase #6	$221.63	11.639%	$247.4255	$247.43	$247.45	$247.40
Purchase #7	$174.91	12.590%	$196.9312	$196.93	$196.95	$196.90
7 purchase totals =	$1,042.07		$1,142.3652	$1,142.35	$1,142.40	$1,142.30