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	$38.76	13.682%	$44.0631	$44.06	$44.05	$44.10
Purchase #2	$109.25	6.266%	$116.0956	$116.10	$116.10	$116.10
Purchase #3	$47.96	4.838%	$50.2803	$50.28	$50.30	$50.30
Purchase #4	$159.83	7.579%	$171.9435	$171.94	$171.95	$171.90
Purchase #5	$221.88	7.441%	$238.3901	$238.39	$238.40	$238.40
Purchase #6	$116.87	10.595%	$129.2524	$129.25	$129.25	$129.30
Purchase #7	$40.86	13.750%	$46.4783	$46.48	$46.50	$46.50
7 purchase totals =	$735.41		$796.5033	$796.50	$796.55	$796.60