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	$210.99	10.808%	$233.7938	$233.79	$233.80	$233.80
Purchase #2	$22.85	11.262%	$25.4234	$25.42	$25.40	$25.40
Purchase #3	$194.27	8.268%	$210.3322	$210.33	$210.35	$210.30
Purchase #4	$142.60	5.828%	$150.9107	$150.91	$150.90	$150.90
Purchase #5	$140.62	7.164%	$150.694	$150.69	$150.70	$150.70
Purchase #6	$120.74	8.872%	$131.4521	$131.45	$131.45	$131.50
Purchase #7	$116.97	10.212%	$128.915	$128.92	$128.90	$128.90
7 purchase totals =	$949.04		$1,031.5212	$1,031.51	$1,031.50	$1,031.50