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	$97.85	13.787%	$111.3406	$111.34	$111.35	$111.30
Purchase #2	$238.98	6.641%	$254.8507	$254.85	$254.85	$254.90
Purchase #3	$179.39	10.129%	$197.5604	$197.56	$197.55	$197.60
Purchase #4	$202.87	6.489%	$216.0342	$216.03	$216.05	$216.00
Purchase #5	$202.59	6.146%	$215.0412	$215.04	$215.05	$215.00
Purchase #6	$104.55	6.189%	$111.0206	$111.02	$111.00	$111.00
Purchase #7	$101.53	10.125%	$111.8099	$111.81	$111.80	$111.80
7 purchase totals =	$1,127.76		$1,217.6576	$1,217.65	$1,217.65	$1,217.60