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	$202.55	11.466%	$225.7744	$225.77	$225.75	$225.80
Purchase #2	$215.27	3.487%	$222.7765	$222.78	$222.80	$222.80
Purchase #3	$224.90	8.726%	$244.5248	$244.52	$244.50	$244.50
Purchase #4	$104.39	9.236%	$114.0315	$114.03	$114.05	$114.00
Purchase #5	$72.68	10.588%	$80.3754	$80.38	$80.40	$80.40
Purchase #6	$145.39	3.546%	$150.5455	$150.55	$150.55	$150.50
Purchase #7	$234.83	12.498%	$264.1791	$264.18	$264.20	$264.20
7 purchase totals =	$1,200.01		$1,302.2072	$1,302.21	$1,302.25	$1,302.20