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	$115.59	9.434%	$126.4948	$126.49	$126.50	$126.50
Purchase #2	$93.59	11.496%	$104.3491	$104.35	$104.35	$104.30
Purchase #3	$94.64	5.398%	$99.7487	$99.75	$99.75	$99.70
Purchase #4	$248.58	10.441%	$274.5342	$274.53	$274.55	$274.50
Purchase #5	$92.59	6.390%	$98.5065	$98.51	$98.50	$98.50
Purchase #6	$200.64	12.313%	$225.3448	$225.34	$225.35	$225.30
Purchase #7	$95.84	6.370%	$101.945	$101.95	$101.95	$101.90
7 purchase totals =	$941.47		$1,030.9231	$1,030.92	$1,030.95	$1,030.70