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	$183.43	10.866%	$203.3615	$203.36	$203.35	$203.40
Purchase #2	$52.97	8.716%	$57.5869	$57.59	$57.60	$57.60
Purchase #3	$197.48	12.663%	$222.4869	$222.49	$222.50	$222.50
Purchase #4	$42.78	13.435%	$48.5275	$48.53	$48.55	$48.50
Purchase #5	$205.25	6.568%	$218.7308	$218.73	$218.75	$218.70
Purchase #6	$100.90	10.486%	$111.4804	$111.48	$111.50	$111.50
Purchase #7	$169.54	5.730%	$179.2546	$179.25	$179.25	$179.30
7 purchase totals =	$952.35		$1,041.4286	$1,041.43	$1,041.50	$1,041.50