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	$210.73	11.261%	$234.4603	$234.46	$234.45	$234.50
Purchase #2	$69.26	9.305%	$75.7046	$75.70	$75.70	$75.70
Purchase #3	$47.92	7.588%	$51.5562	$51.56	$51.55	$51.60
Purchase #4	$177.38	4.548%	$185.4472	$185.45	$185.45	$185.40
Purchase #5	$111.89	10.630%	$123.7839	$123.78	$123.80	$123.80
Purchase #6	$22.89	11.703%	$25.5688	$25.57	$25.55	$25.60
Purchase #7	$86.71	5.714%	$91.6646	$91.66	$91.65	$91.70
7 purchase totals =	$726.78		$788.1856	$788.18	$788.15	$788.30