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	$28.58	13.382%	$32.4046	$32.40	$32.40	$32.40
Purchase #2	$191.46	7.335%	$205.5036	$205.50	$205.50	$205.50
Purchase #3	$189.25	8.417%	$205.1792	$205.18	$205.20	$205.20
Purchase #4	$227.76	10.402%	$251.4516	$251.45	$251.45	$251.50
Purchase #5	$179.67	5.627%	$189.78	$189.78	$189.80	$189.80
Purchase #6	$186.59	7.421%	$200.4368	$200.44	$200.45	$200.40
Purchase #7	$105.49	7.674%	$113.5853	$113.59	$113.60	$113.60
7 purchase totals =	$1,108.80		$1,198.3411	$1,198.34	$1,198.40	$1,198.40