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	$119.89	10.538%	$132.524	$132.52	$132.50	$132.50
Purchase #2	$140.60	11.399%	$156.627	$156.63	$156.65	$156.60
Purchase #3	$27.53	12.844%	$31.066	$31.07	$31.05	$31.10
Purchase #4	$119.71	9.310%	$130.855	$130.86	$130.85	$130.90
Purchase #5	$219.98	12.454%	$247.3763	$247.38	$247.40	$247.40
Purchase #6	$56.97	12.139%	$63.8856	$63.89	$63.90	$63.90
Purchase #7	$168.42	4.248%	$175.5745	$175.57	$175.55	$175.60
7 purchase totals =	$853.10		$937.9084	$937.92	$937.90	$938.00