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	$103.61	12.609%	$116.6742	$116.67	$116.65	$116.70
Purchase #2	$27.48	13.417%	$31.167	$31.17	$31.15	$31.20
Purchase #3	$40.60	7.868%	$43.7944	$43.79	$43.80	$43.80
Purchase #4	$237.46	12.183%	$266.3898	$266.39	$266.40	$266.40
Purchase #5	$20.39	10.591%	$22.5495	$22.55	$22.55	$22.50
Purchase #6	$55.66	6.596%	$59.3313	$59.33	$59.35	$59.30
Purchase #7	$76.48	13.182%	$86.5616	$86.56	$86.55	$86.60
7 purchase totals =	$561.68		$626.4678	$626.46	$626.45	$626.50