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	$210.41	8.172%	$227.6047	$227.60	$227.60	$227.60
Purchase #2	$154.67	10.209%	$170.4603	$170.46	$170.45	$170.50
Purchase #3	$96.56	4.218%	$100.6329	$100.63	$100.65	$100.60
Purchase #4	$55.76	3.167%	$57.5259	$57.53	$57.55	$57.50
Purchase #5	$64.37	12.221%	$72.2367	$72.24	$72.25	$72.20
Purchase #6	$161.40	12.685%	$181.8736	$181.87	$181.85	$181.90
Purchase #7	$133.48	5.133%	$140.3315	$140.33	$140.35	$140.30
7 purchase totals =	$876.65		$950.6656	$950.66	$950.70	$950.60