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	$32.58	13.811%	$37.0796	$37.08	$37.10	$37.10
Purchase #2	$237.81	5.323%	$250.4686	$250.47	$250.45	$250.50
Purchase #3	$179.89	6.661%	$191.8725	$191.87	$191.85	$191.90
Purchase #4	$43.48	5.863%	$46.0292	$46.03	$46.05	$46.00
Purchase #5	$73.89	13.265%	$83.6915	$83.69	$83.70	$83.70
Purchase #6	$236.57	10.650%	$261.7647	$261.76	$261.75	$261.80
Purchase #7	$150.91	9.259%	$164.8828	$164.88	$164.90	$164.90
7 purchase totals =	$955.13		$1,035.7889	$1,035.78	$1,035.80	$1,035.90