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	$29.82	4.785%	$31.2469	$31.25	$31.25	$31.20
Purchase #2	$245.81	3.296%	$253.9119	$253.91	$253.90	$253.90
Purchase #3	$221.90	5.610%	$234.3486	$234.35	$234.35	$234.30
Purchase #4	$110.48	11.765%	$123.478	$123.48	$123.50	$123.50
Purchase #5	$210.61	8.294%	$228.078	$228.08	$228.10	$228.10
Purchase #6	$148.57	10.598%	$164.3154	$164.32	$164.30	$164.30
Purchase #7	$118.49	7.320%	$127.1635	$127.16	$127.15	$127.20
7 purchase totals =	$1,085.68		$1,162.5423	$1,162.55	$1,162.55	$1,162.50