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	$175.86	6.686%	$187.618	$187.62	$187.60	$187.60
Purchase #2	$215.51	10.845%	$238.8821	$238.88	$238.90	$238.90
Purchase #3	$238.25	9.236%	$260.2548	$260.25	$260.25	$260.30
Purchase #4	$40.33	12.123%	$45.2192	$45.22	$45.20	$45.20
Purchase #5	$219.99	5.583%	$232.272	$232.27	$232.25	$232.30
Purchase #6	$189.57	3.554%	$196.3073	$196.31	$196.30	$196.30
Purchase #7	$204.76	13.237%	$231.8641	$231.86	$231.85	$231.90
7 purchase totals =	$1,284.27		$1,392.4175	$1,392.41	$1,392.35	$1,392.50