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	$145.39	3.558%	$150.563	$150.56	$150.55	$150.60
Purchase #2	$228.61	9.280%	$249.825	$249.83	$249.85	$249.80
Purchase #3	$173.94	8.732%	$189.1284	$189.13	$189.15	$189.10
Purchase #4	$153.87	12.161%	$172.5821	$172.58	$172.60	$172.60
Purchase #5	$100.94	12.133%	$113.1871	$113.19	$113.20	$113.20
Purchase #6	$199.28	4.644%	$208.5346	$208.53	$208.55	$208.50
Purchase #7	$90.30	8.683%	$98.1407	$98.14	$98.15	$98.10
7 purchase totals =	$1,092.33		$1,181.9609	$1,181.96	$1,182.05	$1,181.90