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	$184.67	13.605%	$209.7944	$209.79	$209.80	$209.80
Purchase #2	$140.62	5.129%	$147.8324	$147.83	$147.85	$147.80
Purchase #3	$158.54	7.475%	$170.3909	$170.39	$170.40	$170.40
Purchase #4	$191.82	4.221%	$199.9167	$199.92	$199.90	$199.90
Purchase #5	$102.82	9.502%	$112.59	$112.59	$112.60	$112.60
Purchase #6	$7.30	4.282%	$7.6126	$7.61	$7.60	$7.60
Purchase #7	$200.38	8.752%	$217.9173	$217.92	$217.90	$217.90
7 purchase totals =	$986.15		$1,066.0543	$1,066.05	$1,066.05	$1,066.00