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	$42.67	12.241%	$47.8932	$47.89	$47.90	$47.90
Purchase #2	$67.85	8.462%	$73.5915	$73.59	$73.60	$73.60
Purchase #3	$196.91	13.776%	$224.0363	$224.04	$224.05	$224.00
Purchase #4	$210.62	4.185%	$219.4344	$219.43	$219.45	$219.40
Purchase #5	$237.28	13.718%	$269.8301	$269.83	$269.85	$269.80
Purchase #6	$205.52	7.767%	$221.4827	$221.48	$221.50	$221.50
Purchase #7	$200.79	11.406%	$223.6921	$223.69	$223.70	$223.70
7 purchase totals =	$1,161.64		$1,279.9603	$1,279.95	$1,280.05	$1,279.90