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	$144.40	11.868%	$161.5374	$161.54	$161.55	$161.50
Purchase #2	$199.27	8.485%	$216.1781	$216.18	$216.20	$216.20
Purchase #3	$45.71	12.456%	$51.4036	$51.40	$51.40	$51.40
Purchase #4	$38.91	9.314%	$42.5341	$42.53	$42.55	$42.50
Purchase #5	$201.99	11.616%	$225.4532	$225.45	$225.45	$225.50
Purchase #6	$144.50	3.511%	$149.5734	$149.57	$149.55	$149.60
Purchase #7	$178.34	10.154%	$196.4486	$196.45	$196.45	$196.40
7 purchase totals =	$953.12		$1,043.1284	$1,043.12	$1,043.15	$1,043.10