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	$139.78	11.155%	$155.3725	$155.37	$155.35	$155.40
Purchase #2	$123.37	3.130%	$127.2315	$127.23	$127.25	$127.20
Purchase #3	$133.84	4.524%	$139.8949	$139.89	$139.90	$139.90
Purchase #4	$213.58	9.476%	$233.8188	$233.82	$233.80	$233.80
Purchase #5	$160.34	4.598%	$167.7124	$167.71	$167.70	$167.70
Purchase #6	$212.73	4.835%	$223.0155	$223.02	$223.00	$223.00
Purchase #7	$92.39	7.777%	$99.5752	$99.58	$99.60	$99.60
7 purchase totals =	$1,076.03		$1,146.6208	$1,146.62	$1,146.60	$1,146.60