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	$161.92	6.178%	$171.9234	$171.92	$171.90	$171.90
Purchase #2	$81.28	6.361%	$86.4502	$86.45	$86.45	$86.50
Purchase #3	$78.67	8.330%	$85.2232	$85.22	$85.20	$85.20
Purchase #4	$43.65	5.138%	$45.8927	$45.89	$45.90	$45.90
Purchase #5	$209.89	11.791%	$234.6381	$234.64	$234.65	$234.60
Purchase #6	$122.99	11.781%	$137.4795	$137.48	$137.50	$137.50
Purchase #7	$239.93	8.288%	$259.8154	$259.82	$259.80	$259.80
7 purchase totals =	$938.33		$1,021.4225	$1,021.42	$1,021.40	$1,021.40