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	$33.64	7.415%	$36.1344	$36.13	$36.15	$36.10
Purchase #2	$146.94	12.699%	$165.5999	$165.60	$165.60	$165.60
Purchase #3	$123.50	6.409%	$131.4151	$131.42	$131.40	$131.40
Purchase #4	$180.76	3.157%	$186.4666	$186.47	$186.45	$186.50
Purchase #5	$161.56	5.468%	$170.3941	$170.39	$170.40	$170.40
Purchase #6	$226.77	13.827%	$258.1255	$258.13	$258.15	$258.10
Purchase #7	$88.70	13.809%	$100.9486	$100.95	$100.95	$100.90
7 purchase totals =	$961.87		$1,049.0842	$1,049.09	$1,049.10	$1,049.00