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	$172.29	6.614%	$183.6853	$183.69	$183.70	$183.70
Purchase #2	$103.96	7.446%	$111.7009	$111.70	$111.70	$111.70
Purchase #3	$93.96	12.426%	$105.6355	$105.64	$105.65	$105.60
Purchase #4	$66.80	4.219%	$69.6183	$69.62	$69.60	$69.60
Purchase #5	$135.86	6.253%	$144.3553	$144.36	$144.35	$144.40
Purchase #6	$150.33	4.339%	$156.8528	$156.85	$156.85	$156.90
Purchase #7	$98.32	6.693%	$104.9006	$104.90	$104.90	$104.90
7 purchase totals =	$821.52		$876.7487	$876.76	$876.75	$876.80