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	$103.41	6.800%	$110.4419	$110.44	$110.45	$110.40
Purchase #2	$207.61	8.107%	$224.4409	$224.44	$224.45	$224.40
Purchase #3	$229.59	11.259%	$255.4395	$255.44	$255.45	$255.40
Purchase #4	$172.48	4.772%	$180.7107	$180.71	$180.70	$180.70
Purchase #5	$166.54	12.226%	$186.9012	$186.90	$186.90	$186.90
Purchase #6	$63.54	12.418%	$71.4304	$71.43	$71.45	$71.40
Purchase #7	$126.32	12.761%	$142.4397	$142.44	$142.45	$142.40
7 purchase totals =	$1,069.49		$1,171.8043	$1,171.80	$1,171.85	$1,171.60