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	$206.64	7.820%	$222.7992	$222.80	$222.80	$222.80
Purchase #2	$165.95	12.388%	$186.5079	$186.51	$186.50	$186.50
Purchase #3	$82.92	8.576%	$90.0312	$90.03	$90.05	$90.00
Purchase #4	$90.43	11.250%	$100.6034	$100.60	$100.60	$100.60
Purchase #5	$174.49	3.355%	$180.3441	$180.34	$180.35	$180.30
Purchase #6	$176.76	6.681%	$188.5693	$188.57	$188.55	$188.60
Purchase #7	$209.53	8.656%	$227.6669	$227.67	$227.65	$227.70
7 purchase totals =	$1,106.72		$1,196.5220	$1,196.52	$1,196.50	$1,196.50