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	$183.72	10.854%	$203.661	$203.66	$203.65	$203.70
Purchase #2	$89.30	11.259%	$99.3543	$99.35	$99.35	$99.40
Purchase #3	$197.79	13.499%	$224.4897	$224.49	$224.50	$224.50
Purchase #4	$192.53	9.200%	$210.2428	$210.24	$210.25	$210.20
Purchase #5	$165.72	11.549%	$184.859	$184.86	$184.85	$184.90
Purchase #6	$238.92	13.689%	$271.6258	$271.63	$271.65	$271.60
Purchase #7	$27.26	8.542%	$29.5885	$29.59	$29.60	$29.60
7 purchase totals =	$1,095.24		$1,223.8211	$1,223.82	$1,223.85	$1,223.90