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	$187.90	11.155%	$208.8602	$208.86	$208.85	$208.90
Purchase #2	$198.59	8.328%	$215.1286	$215.13	$215.15	$215.10
Purchase #3	$136.82	8.205%	$148.0461	$148.05	$148.05	$148.00
Purchase #4	$91.56	9.872%	$100.5988	$100.60	$100.60	$100.60
Purchase #5	$250.89	6.283%	$266.6534	$266.65	$266.65	$266.70
Purchase #6	$238.40	7.243%	$255.6673	$255.67	$255.65	$255.70
Purchase #7	$102.83	3.429%	$106.356	$106.36	$106.35	$106.40
7 purchase totals =	$1,206.99		$1,301.3104	$1,301.32	$1,301.30	$1,301.40