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	$83.39	10.149%	$91.8533	$91.85	$91.85	$91.90
Purchase #2	$72.58	8.490%	$78.742	$78.74	$78.75	$78.70
Purchase #3	$38.50	12.264%	$43.2216	$43.22	$43.20	$43.20
Purchase #4	$83.44	4.778%	$87.4268	$87.43	$87.45	$87.40
Purchase #5	$22.91	11.297%	$25.4981	$25.50	$25.50	$25.50
Purchase #6	$70.70	11.614%	$78.9111	$78.91	$78.90	$78.90
Purchase #7	$45.57	9.271%	$49.7948	$49.79	$49.80	$49.80
7 purchase totals =	$417.09		$455.4477	$455.44	$455.45	$455.40