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	$12.30	8.560%	$13.3529	$13.35	$13.35	$13.40
Purchase #2	$146.37	12.233%	$164.2754	$164.28	$164.30	$164.30
Purchase #3	$146.93	12.658%	$165.5284	$165.53	$165.55	$165.50
Purchase #4	$161.89	12.565%	$182.2315	$182.23	$182.25	$182.20
Purchase #5	$66.72	9.242%	$72.8863	$72.89	$72.90	$72.90
Purchase #6	$134.83	12.542%	$151.7404	$151.74	$151.75	$151.70
Purchase #7	$235.73	9.317%	$257.693	$257.69	$257.70	$257.70
7 purchase totals =	$904.77		$1,007.7079	$1,007.71	$1,007.80	$1,007.70