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	$180.78	9.863%	$198.6103	$198.61	$198.60	$198.60
Purchase #2	$235.80	4.874%	$247.2929	$247.29	$247.30	$247.30
Purchase #3	$168.68	11.703%	$188.4206	$188.42	$188.40	$188.40
Purchase #4	$47.83	12.856%	$53.979	$53.98	$54.00	$54.00
Purchase #5	$102.43	7.227%	$109.8326	$109.83	$109.85	$109.80
Purchase #6	$104.75	7.844%	$112.9666	$112.97	$112.95	$113.00
Purchase #7	$78.44	8.857%	$85.3874	$85.39	$85.40	$85.40
7 purchase totals =	$918.71		$996.4894	$996.49	$996.50	$996.50