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	$96.70	5.700%	$102.2119	$102.21	$102.20	$102.20
Purchase #2	$106.55	6.386%	$113.3543	$113.35	$113.35	$113.40
Purchase #3	$59.66	13.391%	$67.6491	$67.65	$67.65	$67.60
Purchase #4	$186.52	5.245%	$196.303	$196.30	$196.30	$196.30
Purchase #5	$208.73	4.375%	$217.8619	$217.86	$217.85	$217.90
Purchase #6	$73.77	11.561%	$82.2985	$82.30	$82.30	$82.30
Purchase #7	$244.84	4.752%	$256.4748	$256.47	$256.45	$256.50
7 purchase totals =	$976.77		$1,036.1535	$1,036.14	$1,036.10	$1,036.20