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	$234.56	11.862%	$262.3835	$262.38	$262.40	$262.40
Purchase #2	$183.98	13.368%	$208.5744	$208.57	$208.55	$208.60
Purchase #3	$124.94	11.696%	$139.553	$139.55	$139.55	$139.60
Purchase #4	$29.84	10.105%	$32.8553	$32.86	$32.85	$32.90
Purchase #5	$184.83	13.843%	$210.416	$210.42	$210.40	$210.40
Purchase #6	$54.69	8.576%	$59.3802	$59.38	$59.40	$59.40
Purchase #7	$135.67	6.700%	$144.7599	$144.76	$144.75	$144.80
7 purchase totals =	$948.51		$1,057.9223	$1,057.92	$1,057.90	$1,058.10