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	$56.77	8.614%	$61.6602	$61.66	$61.65	$61.70
Purchase #2	$168.93	9.852%	$185.573	$185.57	$185.55	$185.60
Purchase #3	$99.37	8.221%	$107.5392	$107.54	$107.55	$107.50
Purchase #4	$105.99	3.157%	$109.3361	$109.34	$109.35	$109.30
Purchase #5	$126.53	12.742%	$142.6525	$142.65	$142.65	$142.70
Purchase #6	$107.46	11.612%	$119.9383	$119.94	$119.95	$119.90
Purchase #7	$160.83	13.694%	$182.8541	$182.85	$182.85	$182.90
7 purchase totals =	$825.88		$909.5534	$909.55	$909.55	$909.60