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	$186.74	12.148%	$209.4252	$209.43	$209.45	$209.40
Purchase #2	$85.46	4.330%	$89.1604	$89.16	$89.15	$89.20
Purchase #3	$25.87	3.517%	$26.7798	$26.78	$26.80	$26.80
Purchase #4	$203.46	3.472%	$210.5241	$210.52	$210.50	$210.50
Purchase #5	$176.47	13.495%	$200.2846	$200.28	$200.30	$200.30
Purchase #6	$189.26	12.267%	$212.4765	$212.48	$212.50	$212.50
Purchase #7	$45.96	4.210%	$47.8949	$47.89	$47.90	$47.90
7 purchase totals =	$913.22		$996.5455	$996.54	$996.60	$996.60