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	$102.80	10.799%	$113.9014	$113.90	$113.90	$113.90
Purchase #2	$52.70	13.109%	$59.6084	$59.61	$59.60	$59.60
Purchase #3	$204.89	11.109%	$227.6512	$227.65	$227.65	$227.70
Purchase #4	$127.37	6.602%	$135.779	$135.78	$135.80	$135.80
Purchase #5	$106.32	6.522%	$113.2542	$113.25	$113.25	$113.30
Purchase #6	$178.59	11.324%	$198.8135	$198.81	$198.80	$198.80
Purchase #7	$136.42	11.824%	$152.5503	$152.55	$152.55	$152.60
7 purchase totals =	$909.09		$1,001.5580	$1,001.55	$1,001.55	$1,001.70