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	$173.54	5.350%	$182.8244	$182.82	$182.80	$182.80
Purchase #2	$92.52	6.547%	$98.5773	$98.58	$98.60	$98.60
Purchase #3	$87.60	3.794%	$90.9235	$90.92	$90.90	$90.90
Purchase #4	$89.45	13.450%	$101.481	$101.48	$101.50	$101.50
Purchase #5	$233.48	9.693%	$256.1112	$256.11	$256.10	$256.10
Purchase #6	$217.69	7.537%	$234.0973	$234.10	$234.10	$234.10
Purchase #7	$137.56	9.653%	$150.8387	$150.84	$150.85	$150.80
7 purchase totals =	$1,031.84		$1,114.8534	$1,114.85	$1,114.85	$1,114.80