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	$195.39	9.314%	$213.5886	$213.59	$213.60	$213.60
Purchase #2	$99.50	12.635%	$112.0718	$112.07	$112.05	$112.10
Purchase #3	$66.76	4.563%	$69.8063	$69.81	$69.80	$69.80
Purchase #4	$246.67	9.344%	$269.7188	$269.72	$269.70	$269.70
Purchase #5	$40.26	6.639%	$42.9329	$42.93	$42.95	$42.90
Purchase #6	$38.97	12.523%	$43.8502	$43.85	$43.85	$43.90
Purchase #7	$163.52	13.696%	$185.9157	$185.92	$185.90	$185.90
7 purchase totals =	$851.07		$937.8843	$937.89	$937.85	$937.90