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	$235.50	8.635%	$255.8354	$255.84	$255.85	$255.80
Purchase #2	$108.64	8.776%	$118.1742	$118.17	$118.15	$118.20
Purchase #3	$84.80	7.342%	$91.026	$91.03	$91.05	$91.00
Purchase #4	$78.41	5.309%	$82.5728	$82.57	$82.55	$82.60
Purchase #5	$108.29	3.836%	$112.444	$112.44	$112.45	$112.40
Purchase #6	$214.66	3.804%	$222.8257	$222.83	$222.85	$222.80
Purchase #7	$209.36	9.766%	$229.8061	$229.81	$229.80	$229.80
7 purchase totals =	$1,039.66		$1,112.6842	$1,112.69	$1,112.70	$1,112.60