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	$79.57	12.274%	$89.3364	$89.34	$89.35	$89.30
Purchase #2	$63.72	9.209%	$69.588	$69.59	$69.60	$69.60
Purchase #3	$202.83	6.484%	$215.9815	$215.98	$216.00	$216.00
Purchase #4	$34.48	12.658%	$38.8445	$38.84	$38.85	$38.80
Purchase #5	$184.82	13.418%	$209.6191	$209.62	$209.60	$209.60
Purchase #6	$201.68	7.488%	$216.7818	$216.78	$216.80	$216.80
Purchase #7	$205.52	7.716%	$221.3779	$221.38	$221.40	$221.40
7 purchase totals =	$972.62		$1,061.5292	$1,061.53	$1,061.60	$1,061.50