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	$88.80	9.648%	$97.3674	$97.37	$97.35	$97.40
Purchase #2	$90.29	4.324%	$94.1941	$94.19	$94.20	$94.20
Purchase #3	$92.44	12.334%	$103.8415	$103.84	$103.85	$103.80
Purchase #4	$172.75	11.342%	$192.3433	$192.34	$192.35	$192.30
Purchase #5	$223.52	4.192%	$232.89	$232.89	$232.90	$232.90
Purchase #6	$221.33	9.155%	$241.5928	$241.59	$241.60	$241.60
Purchase #7	$90.46	9.770%	$99.2979	$99.30	$99.30	$99.30
7 purchase totals =	$979.59		$1,061.5270	$1,061.52	$1,061.55	$1,061.50