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	$143.53	4.860%	$150.5056	$150.51	$150.50	$150.50
Purchase #2	$107.87	10.170%	$118.8404	$118.84	$118.85	$118.80
Purchase #3	$209.89	3.622%	$217.4922	$217.49	$217.50	$217.50
Purchase #4	$38.70	10.414%	$42.7302	$42.73	$42.75	$42.70
Purchase #5	$6.92	12.503%	$7.7852	$7.79	$7.80	$7.80
Purchase #6	$250.47	3.542%	$259.3416	$259.34	$259.35	$259.30
Purchase #7	$195.63	11.145%	$217.433	$217.43	$217.45	$217.40
7 purchase totals =	$953.01		$1,014.1282	$1,014.13	$1,014.20	$1,014.00