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	$92.67	11.802%	$103.6069	$103.61	$103.60	$103.60
Purchase #2	$33.26	3.211%	$34.328	$34.33	$34.35	$34.30
Purchase #3	$59.51	13.328%	$67.4415	$67.44	$67.45	$67.40
Purchase #4	$250.77	12.270%	$281.5395	$281.54	$281.55	$281.50
Purchase #5	$84.83	3.526%	$87.8211	$87.82	$87.80	$87.80
Purchase #6	$240.27	10.601%	$265.741	$265.74	$265.75	$265.70
Purchase #7	$126.85	12.540%	$142.757	$142.76	$142.75	$142.80
7 purchase totals =	$888.16		$983.2350	$983.24	$983.25	$983.10