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	$241.58	5.655%	$255.2413	$255.24	$255.25	$255.20
Purchase #2	$88.57	13.580%	$100.5978	$100.60	$100.60	$100.60
Purchase #3	$150.47	12.622%	$169.4623	$169.46	$169.45	$169.50
Purchase #4	$148.76	4.432%	$155.353	$155.35	$155.35	$155.40
Purchase #5	$104.47	5.659%	$110.382	$110.38	$110.40	$110.40
Purchase #6	$97.46	12.757%	$109.893	$109.89	$109.90	$109.90
Purchase #7	$193.73	13.227%	$219.3547	$219.35	$219.35	$219.40
7 purchase totals =	$1,025.04		$1,120.2841	$1,120.27	$1,120.30	$1,120.40