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	$64.40	8.764%	$70.044	$70.04	$70.05	$70.00
Purchase #2	$45.28	12.648%	$51.007	$51.01	$51.00	$51.00
Purchase #3	$135.38	6.495%	$144.1729	$144.17	$144.15	$144.20
Purchase #4	$123.71	6.587%	$131.8588	$131.86	$131.85	$131.90
Purchase #5	$193.67	5.293%	$203.921	$203.92	$203.90	$203.90
Purchase #6	$10.28	11.807%	$11.4938	$11.49	$11.50	$11.50
Purchase #7	$244.33	10.462%	$269.8918	$269.89	$269.90	$269.90
7 purchase totals =	$817.05		$882.3893	$882.38	$882.35	$882.40