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	$95.38	11.476%	$106.3258	$106.33	$106.35	$106.30
Purchase #2	$29.46	13.289%	$33.3749	$33.37	$33.35	$33.40
Purchase #3	$60.29	5.337%	$63.5077	$63.51	$63.50	$63.50
Purchase #4	$75.48	12.855%	$85.183	$85.18	$85.20	$85.20
Purchase #5	$139.59	11.850%	$156.1314	$156.13	$156.15	$156.10
Purchase #6	$196.90	13.833%	$224.1372	$224.14	$224.15	$224.10
Purchase #7	$66.81	9.487%	$73.1483	$73.15	$73.15	$73.10
7 purchase totals =	$663.91		$741.8083	$741.81	$741.85	$741.70