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	$10.63	7.547%	$11.4322	$11.43	$11.45	$11.40
Purchase #2	$71.57	11.102%	$79.5157	$79.52	$79.50	$79.50
Purchase #3	$143.35	8.437%	$155.4444	$155.44	$155.45	$155.40
Purchase #4	$142.26	9.165%	$155.2981	$155.30	$155.30	$155.30
Purchase #5	$80.27	6.283%	$85.3134	$85.31	$85.30	$85.30
Purchase #6	$101.94	9.401%	$111.5234	$111.52	$111.50	$111.50
Purchase #7	$13.96	6.407%	$14.8544	$14.85	$14.85	$14.90
7 purchase totals =	$563.98		$613.3816	$613.37	$613.35	$613.30