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	$230.54	4.514%	$240.9466	$240.95	$240.95	$240.90
Purchase #2	$79.41	3.683%	$82.3347	$82.33	$82.35	$82.30
Purchase #3	$222.51	11.648%	$248.428	$248.43	$248.45	$248.40
Purchase #4	$215.77	7.318%	$231.56	$231.56	$231.55	$231.60
Purchase #5	$16.70	4.643%	$17.4754	$17.48	$17.50	$17.50
Purchase #6	$131.92	3.495%	$136.5306	$136.53	$136.55	$136.50
Purchase #7	$69.44	12.691%	$78.2526	$78.25	$78.25	$78.30
7 purchase totals =	$966.29		$1,035.5279	$1,035.53	$1,035.60	$1,035.50