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	$209.75	6.112%	$222.5699	$222.57	$222.55	$222.60
Purchase #2	$178.96	12.156%	$200.7144	$200.71	$200.70	$200.70
Purchase #3	$121.42	12.546%	$136.6534	$136.65	$136.65	$136.70
Purchase #4	$100.53	11.755%	$112.3473	$112.35	$112.35	$112.30
Purchase #5	$38.39	11.133%	$42.664	$42.66	$42.65	$42.70
Purchase #6	$172.70	3.440%	$178.6409	$178.64	$178.65	$178.60
Purchase #7	$242.61	5.460%	$255.8565	$255.86	$255.85	$255.90
7 purchase totals =	$1,064.36		$1,149.4464	$1,149.44	$1,149.40	$1,149.50