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	$224.44	10.143%	$247.2049	$247.20	$247.20	$247.20
Purchase #2	$33.28	8.306%	$36.0442	$36.04	$36.05	$36.00
Purchase #3	$41.48	3.513%	$42.9372	$42.94	$42.95	$42.90
Purchase #4	$130.59	8.628%	$141.8573	$141.86	$141.85	$141.90
Purchase #5	$52.82	12.538%	$59.4426	$59.44	$59.45	$59.40
Purchase #6	$174.82	12.583%	$196.8176	$196.82	$196.80	$196.80
Purchase #7	$162.57	11.798%	$181.75	$181.75	$181.75	$181.80
7 purchase totals =	$820.00		$906.0538	$906.05	$906.05	$906.00