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	$156.57	7.413%	$168.1765	$168.18	$168.20	$168.20
Purchase #2	$242.80	11.505%	$270.7341	$270.73	$270.75	$270.70
Purchase #3	$56.81	4.665%	$59.4602	$59.46	$59.45	$59.50
Purchase #4	$45.81	3.703%	$47.5063	$47.51	$47.50	$47.50
Purchase #5	$37.38	11.215%	$41.5722	$41.57	$41.55	$41.60
Purchase #6	$30.45	3.585%	$31.5416	$31.54	$31.55	$31.50
Purchase #7	$240.97	9.504%	$263.8718	$263.87	$263.85	$263.90
7 purchase totals =	$810.79		$882.8627	$882.86	$882.85	$882.90