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	$86.41	7.176%	$92.6108	$92.61	$92.60	$92.60
Purchase #2	$207.83	12.328%	$233.4513	$233.45	$233.45	$233.50
Purchase #3	$35.74	10.335%	$39.4337	$39.43	$39.45	$39.40
Purchase #4	$80.94	5.557%	$85.4378	$85.44	$85.45	$85.40
Purchase #5	$189.38	13.166%	$214.3138	$214.31	$214.30	$214.30
Purchase #6	$187.77	11.779%	$209.8874	$209.89	$209.90	$209.90
Purchase #7	$246.56	8.188%	$266.7483	$266.75	$266.75	$266.70
7 purchase totals =	$1,034.63		$1,141.8831	$1,141.88	$1,141.90	$1,141.80