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	$221.93	3.221%	$229.0784	$229.08	$229.10	$229.10
Purchase #2	$118.78	10.421%	$131.1581	$131.16	$131.15	$131.20
Purchase #3	$38.31	8.405%	$41.53	$41.53	$41.55	$41.50
Purchase #4	$135.83	6.385%	$144.5027	$144.50	$144.50	$144.50
Purchase #5	$76.37	9.264%	$83.4449	$83.44	$83.45	$83.40
Purchase #6	$65.90	6.503%	$70.1855	$70.19	$70.20	$70.20
Purchase #7	$95.53	8.457%	$103.609	$103.61	$103.60	$103.60
7 purchase totals =	$752.65		$803.5086	$803.51	$803.55	$803.50