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	$220.77	7.404%	$237.1158	$237.12	$237.10	$237.10
Purchase #2	$159.54	12.379%	$179.2895	$179.29	$179.30	$179.30
Purchase #3	$22.60	10.731%	$25.0252	$25.03	$25.05	$25.00
Purchase #4	$140.82	5.422%	$148.4553	$148.46	$148.45	$148.50
Purchase #5	$104.97	10.813%	$116.3204	$116.32	$116.30	$116.30
Purchase #6	$179.43	3.498%	$185.7065	$185.71	$185.70	$185.70
Purchase #7	$73.49	12.309%	$82.5359	$82.54	$82.55	$82.50
7 purchase totals =	$901.62		$974.4486	$974.47	$974.45	$974.40