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	$158.85	12.704%	$179.0303	$179.03	$179.05	$179.00
Purchase #2	$83.66	9.861%	$91.9097	$91.91	$91.90	$91.90
Purchase #3	$34.96	7.250%	$37.4946	$37.49	$37.50	$37.50
Purchase #4	$88.38	6.799%	$94.389	$94.39	$94.40	$94.40
Purchase #5	$209.86	5.112%	$220.588	$220.59	$220.60	$220.60
Purchase #6	$213.47	7.449%	$229.3714	$229.37	$229.35	$229.40
Purchase #7	$239.74	6.398%	$255.0786	$255.08	$255.10	$255.10
7 purchase totals =	$1,028.92		$1,107.8616	$1,107.86	$1,107.90	$1,107.90