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	$198.34	10.345%	$218.8583	$218.86	$218.85	$218.90
Purchase #2	$179.28	13.762%	$203.9525	$203.95	$203.95	$204.00
Purchase #3	$31.59	3.207%	$32.6031	$32.60	$32.60	$32.60
Purchase #4	$9.86	11.107%	$10.9552	$10.96	$10.95	$11.00
Purchase #5	$176.61	4.711%	$184.9301	$184.93	$184.95	$184.90
Purchase #6	$76.87	10.748%	$85.132	$85.13	$85.15	$85.10
Purchase #7	$91.56	3.641%	$94.8937	$94.89	$94.90	$94.90
7 purchase totals =	$764.11		$831.3249	$831.32	$831.35	$831.40