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	$57.38	3.744%	$59.5283	$59.53	$59.55	$59.50
Purchase #2	$167.82	9.369%	$183.5431	$183.54	$183.55	$183.50
Purchase #3	$165.47	3.865%	$171.8654	$171.87	$171.85	$171.90
Purchase #4	$137.75	9.664%	$151.0622	$151.06	$151.05	$151.10
Purchase #5	$24.57	7.443%	$26.3987	$26.40	$26.40	$26.40
Purchase #6	$73.58	9.458%	$80.5392	$80.54	$80.55	$80.50
Purchase #7	$13.33	11.434%	$14.8542	$14.85	$14.85	$14.90
7 purchase totals =	$639.90		$687.7911	$687.79	$687.80	$687.80