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	$232.90	8.208%	$252.0164	$252.02	$252.00	$252.00
Purchase #2	$37.85	11.292%	$42.124	$42.12	$42.10	$42.10
Purchase #3	$80.57	7.379%	$86.5153	$86.52	$86.50	$86.50
Purchase #4	$194.71	11.751%	$217.5904	$217.59	$217.60	$217.60
Purchase #5	$165.28	8.454%	$179.2528	$179.25	$179.25	$179.30
Purchase #6	$75.37	3.589%	$78.075	$78.08	$78.10	$78.10
Purchase #7	$219.66	9.540%	$240.6156	$240.62	$240.60	$240.60
7 purchase totals =	$1,006.34		$1,096.1895	$1,096.20	$1,096.15	$1,096.20