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	$124.69	11.873%	$139.4944	$139.49	$139.50	$139.50
Purchase #2	$178.42	10.130%	$196.4939	$196.49	$196.50	$196.50
Purchase #3	$244.31	7.785%	$263.3295	$263.33	$263.35	$263.30
Purchase #4	$78.51	6.107%	$83.3046	$83.30	$83.30	$83.30
Purchase #5	$109.25	11.622%	$121.947	$121.95	$121.95	$121.90
Purchase #6	$162.50	8.246%	$175.8998	$175.90	$175.90	$175.90
Purchase #7	$162.56	6.757%	$173.5442	$173.54	$173.55	$173.50
7 purchase totals =	$1,060.24		$1,154.0134	$1,154.00	$1,154.05	$1,153.90