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	$110.63	6.481%	$117.7999	$117.80	$117.80	$117.80
Purchase #2	$76.50	12.604%	$86.1421	$86.14	$86.15	$86.10
Purchase #3	$217.85	5.518%	$229.871	$229.87	$229.85	$229.90
Purchase #4	$197.36	4.386%	$206.0162	$206.02	$206.00	$206.00
Purchase #5	$155.43	8.667%	$168.9011	$168.90	$168.90	$168.90
Purchase #6	$101.94	9.773%	$111.9026	$111.90	$111.90	$111.90
Purchase #7	$142.70	6.353%	$151.7657	$151.77	$151.75	$151.80
7 purchase totals =	$1,002.41		$1,072.3986	$1,072.40	$1,072.35	$1,072.40