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	$113.61	13.832%	$129.3245	$129.32	$129.30	$129.30
Purchase #2	$145.78	12.863%	$164.5317	$164.53	$164.55	$164.50
Purchase #3	$183.66	8.838%	$199.8919	$199.89	$199.90	$199.90
Purchase #4	$217.50	9.603%	$238.3865	$238.39	$238.40	$238.40
Purchase #5	$170.47	11.347%	$189.8132	$189.81	$189.80	$189.80
Purchase #6	$167.43	6.331%	$178.03	$178.03	$178.05	$178.00
Purchase #7	$44.41	13.337%	$50.333	$50.33	$50.35	$50.30
7 purchase totals =	$1,042.86		$1,150.3108	$1,150.30	$1,150.35	$1,150.20