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	$129.41	5.255%	$136.2105	$136.21	$136.20	$136.20
Purchase #2	$70.88	9.624%	$77.7015	$77.70	$77.70	$77.70
Purchase #3	$172.65	4.851%	$181.0253	$181.03	$181.05	$181.00
Purchase #4	$218.65	5.675%	$231.0584	$231.06	$231.05	$231.10
Purchase #5	$123.66	12.807%	$139.4971	$139.50	$139.50	$139.50
Purchase #6	$201.51	4.223%	$210.0198	$210.02	$210.00	$210.00
Purchase #7	$104.54	6.547%	$111.3842	$111.38	$111.40	$111.40
7 purchase totals =	$1,021.30		$1,086.8968	$1,086.90	$1,086.90	$1,086.90