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	$40.59	3.657%	$42.0744	$42.07	$42.05	$42.10
Purchase #2	$206.51	8.502%	$224.0675	$224.07	$224.05	$224.10
Purchase #3	$238.94	11.284%	$265.902	$265.90	$265.90	$265.90
Purchase #4	$201.91	7.725%	$217.5075	$217.51	$217.50	$217.50
Purchase #5	$56.27	3.542%	$58.2631	$58.26	$58.25	$58.30
Purchase #6	$99.38	12.593%	$111.8949	$111.89	$111.90	$111.90
Purchase #7	$145.28	13.758%	$165.2676	$165.27	$165.25	$165.30
7 purchase totals =	$988.88		$1,084.9770	$1,084.97	$1,084.90	$1,085.10