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	$169.88	6.833%	$181.4879	$181.49	$181.50	$181.50
Purchase #2	$119.68	13.672%	$136.0426	$136.04	$136.05	$136.00
Purchase #3	$231.91	12.346%	$260.5416	$260.54	$260.55	$260.50
Purchase #4	$51.84	5.119%	$54.4937	$54.49	$54.50	$54.50
Purchase #5	$183.73	3.551%	$190.2543	$190.25	$190.25	$190.30
Purchase #6	$64.76	11.651%	$72.3052	$72.31	$72.30	$72.30
Purchase #7	$104.89	12.807%	$118.3233	$118.32	$118.30	$118.30
7 purchase totals =	$926.69		$1,013.4486	$1,013.44	$1,013.45	$1,013.40