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	$213.53	4.297%	$222.7054	$222.71	$222.70	$222.70
Purchase #2	$156.25	9.269%	$170.7328	$170.73	$170.75	$170.70
Purchase #3	$194.71	7.768%	$209.8351	$209.84	$209.85	$209.80
Purchase #4	$130.65	10.571%	$144.461	$144.46	$144.45	$144.50
Purchase #5	$108.32	13.611%	$123.0634	$123.06	$123.05	$123.10
Purchase #6	$242.44	9.825%	$266.2597	$266.26	$266.25	$266.30
Purchase #7	$65.82	8.564%	$71.4568	$71.46	$71.45	$71.50
7 purchase totals =	$1,111.72		$1,208.5142	$1,208.52	$1,208.50	$1,208.60