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	$218.73	10.236%	$241.1192	$241.12	$241.10	$241.10
Purchase #2	$61.43	11.181%	$68.2985	$68.30	$68.30	$68.30
Purchase #3	$90.77	13.341%	$102.8796	$102.88	$102.90	$102.90
Purchase #4	$78.82	11.765%	$88.0932	$88.09	$88.10	$88.10
Purchase #5	$192.64	12.166%	$216.0766	$216.08	$216.10	$216.10
Purchase #6	$91.76	8.127%	$99.2173	$99.22	$99.20	$99.20
Purchase #7	$101.36	3.750%	$105.161	$105.16	$105.15	$105.20
7 purchase totals =	$835.51		$920.8454	$920.85	$920.85	$920.90