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	$197.53	10.154%	$217.5872	$217.59	$217.60	$217.60
Purchase #2	$201.73	10.679%	$223.2727	$223.27	$223.25	$223.30
Purchase #3	$109.63	4.540%	$114.6072	$114.61	$114.60	$114.60
Purchase #4	$37.58	12.380%	$42.2324	$42.23	$42.25	$42.20
Purchase #5	$215.96	5.791%	$228.4662	$228.47	$228.45	$228.50
Purchase #6	$97.66	4.288%	$101.8477	$101.85	$101.85	$101.80
Purchase #7	$160.97	5.215%	$169.3646	$169.36	$169.35	$169.40
7 purchase totals =	$1,021.06		$1,097.3780	$1,097.38	$1,097.35	$1,097.40