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	$10.93	9.396%	$11.957	$11.96	$11.95	$12.00
Purchase #2	$99.59	10.172%	$109.7203	$109.72	$109.70	$109.70
Purchase #3	$91.81	7.105%	$98.3331	$98.33	$98.35	$98.30
Purchase #4	$71.64	6.531%	$76.3188	$76.32	$76.30	$76.30
Purchase #5	$195.91	6.247%	$208.1485	$208.15	$208.15	$208.10
Purchase #6	$238.43	3.602%	$247.0182	$247.02	$247.00	$247.00
Purchase #7	$118.87	4.235%	$123.9041	$123.90	$123.90	$123.90
7 purchase totals =	$827.18		$875.4000	$875.40	$875.35	$875.30