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	$120.66	5.653%	$127.4809	$127.48	$127.50	$127.50
Purchase #2	$75.82	9.429%	$82.9691	$82.97	$82.95	$83.00
Purchase #3	$94.47	4.655%	$98.8676	$98.87	$98.85	$98.90
Purchase #4	$244.77	4.842%	$256.6218	$256.62	$256.60	$256.60
Purchase #5	$18.88	11.649%	$21.0793	$21.08	$21.10	$21.10
Purchase #6	$156.29	7.453%	$167.9383	$167.94	$167.95	$167.90
Purchase #7	$233.67	12.229%	$262.2455	$262.25	$262.25	$262.20
7 purchase totals =	$944.56		$1,017.2025	$1,017.21	$1,017.20	$1,017.20