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	$59.64	11.333%	$66.399	$66.40	$66.40	$66.40
Purchase #2	$150.45	11.833%	$168.2527	$168.25	$168.25	$168.30
Purchase #3	$241.44	13.184%	$273.2714	$273.27	$273.25	$273.30
Purchase #4	$78.93	8.411%	$85.5688	$85.57	$85.55	$85.60
Purchase #5	$249.38	4.165%	$259.7667	$259.77	$259.75	$259.80
Purchase #6	$215.25	10.105%	$237.001	$237.00	$237.00	$237.00
Purchase #7	$165.87	5.682%	$175.2947	$175.29	$175.30	$175.30
7 purchase totals =	$1,160.96		$1,265.5543	$1,265.55	$1,265.50	$1,265.70