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	$53.90	7.432%	$57.9058	$57.91	$57.90	$57.90
Purchase #2	$21.60	8.480%	$23.4317	$23.43	$23.45	$23.40
Purchase #3	$147.74	11.589%	$164.8616	$164.86	$164.85	$164.90
Purchase #4	$159.46	7.508%	$171.4323	$171.43	$171.45	$171.40
Purchase #5	$147.81	6.440%	$157.329	$157.33	$157.35	$157.30
Purchase #6	$249.44	8.466%	$270.5576	$270.56	$270.55	$270.60
Purchase #7	$177.80	6.801%	$189.8922	$189.89	$189.90	$189.90
7 purchase totals =	$957.75		$1,035.4102	$1,035.41	$1,035.45	$1,035.40