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	$179.32	7.227%	$192.2795	$192.28	$192.30	$192.30
Purchase #2	$160.33	13.264%	$181.5962	$181.60	$181.60	$181.60
Purchase #3	$50.98	13.669%	$57.9485	$57.95	$57.95	$57.90
Purchase #4	$13.50	13.477%	$15.3194	$15.32	$15.30	$15.30
Purchase #5	$29.67	10.873%	$32.896	$32.90	$32.90	$32.90
Purchase #6	$37.86	9.713%	$41.5373	$41.54	$41.55	$41.50
Purchase #7	$104.56	8.511%	$113.4591	$113.46	$113.45	$113.50
7 purchase totals =	$576.22		$635.0360	$635.05	$635.05	$635.00