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	$189.42	11.588%	$211.37	$211.37	$211.35	$211.40
Purchase #2	$115.85	6.865%	$123.8031	$123.80	$123.80	$123.80
Purchase #3	$40.48	7.469%	$43.5035	$43.50	$43.50	$43.50
Purchase #4	$80.53	11.741%	$89.985	$89.99	$90.00	$90.00
Purchase #5	$57.79	13.266%	$65.4564	$65.46	$65.45	$65.50
Purchase #6	$118.61	11.367%	$132.0924	$132.09	$132.10	$132.10
Purchase #7	$183.67	13.545%	$208.5481	$208.55	$208.55	$208.50
7 purchase totals =	$786.35		$874.7585	$874.76	$874.75	$874.80