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	$109.96	5.287%	$115.7736	$115.77	$115.75	$115.80
Purchase #2	$193.57	3.391%	$200.134	$200.13	$200.15	$200.10
Purchase #3	$211.85	5.212%	$222.8916	$222.89	$222.90	$222.90
Purchase #4	$68.58	6.173%	$72.8134	$72.81	$72.80	$72.80
Purchase #5	$202.68	7.564%	$218.0107	$218.01	$218.00	$218.00
Purchase #6	$155.94	11.280%	$173.53	$173.53	$173.55	$173.50
Purchase #7	$172.38	13.387%	$195.4565	$195.46	$195.45	$195.50
7 purchase totals =	$1,114.96		$1,198.6098	$1,198.60	$1,198.60	$1,198.60