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	$110.38	3.686%	$114.4486	$114.45	$114.45	$114.40
Purchase #2	$172.77	6.780%	$184.4838	$184.48	$184.50	$184.50
Purchase #3	$44.41	11.354%	$49.4523	$49.45	$49.45	$49.50
Purchase #4	$145.61	8.802%	$158.4266	$158.43	$158.45	$158.40
Purchase #5	$120.36	6.168%	$127.7838	$127.78	$127.80	$127.80
Purchase #6	$113.41	7.375%	$121.774	$121.77	$121.75	$121.80
Purchase #7	$137.48	7.824%	$148.2364	$148.24	$148.25	$148.20
7 purchase totals =	$844.42		$904.6055	$904.60	$904.65	$904.60