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	$206.60	13.163%	$233.7948	$233.79	$233.80	$233.80
Purchase #2	$74.60	5.296%	$78.5508	$78.55	$78.55	$78.60
Purchase #3	$171.59	11.182%	$190.7772	$190.78	$190.80	$190.80
Purchase #4	$148.64	11.639%	$165.9402	$165.94	$165.95	$165.90
Purchase #5	$114.71	13.436%	$130.1224	$130.12	$130.10	$130.10
Purchase #6	$96.50	11.249%	$107.3553	$107.36	$107.35	$107.40
Purchase #7	$224.91	9.383%	$246.0133	$246.01	$246.00	$246.00
7 purchase totals =	$1,037.55		$1,152.5540	$1,152.55	$1,152.55	$1,152.60