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	$59.89	9.136%	$65.3616	$65.36	$65.35	$65.40
Purchase #2	$205.40	12.562%	$231.2023	$231.20	$231.20	$231.20
Purchase #3	$48.43	12.681%	$54.5714	$54.57	$54.55	$54.60
Purchase #4	$35.49	5.134%	$37.3121	$37.31	$37.30	$37.30
Purchase #5	$81.96	6.851%	$87.5751	$87.58	$87.60	$87.60
Purchase #6	$161.98	12.716%	$182.5774	$182.58	$182.60	$182.60
Purchase #7	$86.41	9.117%	$94.288	$94.29	$94.30	$94.30
7 purchase totals =	$679.56		$752.8879	$752.89	$752.90	$753.00