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	$168.38	7.266%	$180.6145	$180.61	$180.60	$180.60
Purchase #2	$236.25	10.683%	$261.4886	$261.49	$261.50	$261.50
Purchase #3	$243.85	4.117%	$253.8893	$253.89	$253.90	$253.90
Purchase #4	$194.39	8.735%	$211.37	$211.37	$211.35	$211.40
Purchase #5	$63.42	6.348%	$67.4459	$67.45	$67.45	$67.40
Purchase #6	$40.27	9.520%	$44.1037	$44.10	$44.10	$44.10
Purchase #7	$89.66	4.126%	$93.3594	$93.36	$93.35	$93.40
7 purchase totals =	$1,036.22		$1,112.2714	$1,112.27	$1,112.25	$1,112.30