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	$174.90	13.704%	$198.8683	$198.87	$198.85	$198.90
Purchase #2	$90.37	13.679%	$102.7317	$102.73	$102.75	$102.70
Purchase #3	$33.91	4.748%	$35.52	$35.52	$35.50	$35.50
Purchase #4	$137.30	10.820%	$152.1559	$152.16	$152.15	$152.20
Purchase #5	$213.91	3.528%	$221.4567	$221.46	$221.45	$221.50
Purchase #6	$238.46	9.661%	$261.4976	$261.50	$261.50	$261.50
Purchase #7	$20.76	3.820%	$21.553	$21.55	$21.55	$21.60
7 purchase totals =	$909.61		$993.7832	$993.79	$993.75	$993.90