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	$42.49	7.147%	$45.5268	$45.53	$45.55	$45.50
Purchase #2	$168.30	9.560%	$184.3895	$184.39	$184.40	$184.40
Purchase #3	$18.29	7.843%	$19.7245	$19.72	$19.70	$19.70
Purchase #4	$74.40	5.299%	$78.3425	$78.34	$78.35	$78.30
Purchase #5	$105.58	13.523%	$119.8576	$119.86	$119.85	$119.90
Purchase #6	$215.59	3.403%	$222.9265	$222.93	$222.95	$222.90
Purchase #7	$240.89	13.632%	$273.7281	$273.73	$273.75	$273.70
7 purchase totals =	$865.54		$944.4955	$944.50	$944.55	$944.40