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	$218.87	4.696%	$229.1481	$229.15	$229.15	$229.10
Purchase #2	$29.32	4.343%	$30.5934	$30.59	$30.60	$30.60
Purchase #3	$249.39	3.319%	$257.6673	$257.67	$257.65	$257.70
Purchase #4	$151.61	13.626%	$172.2684	$172.27	$172.25	$172.30
Purchase #5	$70.32	6.505%	$74.8943	$74.89	$74.90	$74.90
Purchase #6	$150.49	6.698%	$160.5698	$160.57	$160.55	$160.60
Purchase #7	$52.72	12.419%	$59.2673	$59.27	$59.25	$59.30
7 purchase totals =	$922.72		$984.4086	$984.41	$984.35	$984.50