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	$208.45	10.591%	$230.5269	$230.53	$230.55	$230.50
Purchase #2	$109.88	8.322%	$119.0242	$119.02	$119.00	$119.00
Purchase #3	$206.69	11.242%	$229.9261	$229.93	$229.95	$229.90
Purchase #4	$107.82	12.334%	$121.1185	$121.12	$121.10	$121.10
Purchase #5	$88.38	11.814%	$98.8212	$98.82	$98.80	$98.80
Purchase #6	$151.89	10.755%	$168.2258	$168.23	$168.25	$168.20
Purchase #7	$168.48	11.758%	$188.2899	$188.29	$188.30	$188.30
7 purchase totals =	$1,041.59		$1,155.9326	$1,155.94	$1,155.95	$1,155.80