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	$77.52	9.115%	$84.5859	$84.59	$84.60	$84.60
Purchase #2	$50.53	8.815%	$54.9842	$54.98	$55.00	$55.00
Purchase #3	$50.78	6.816%	$54.2412	$54.24	$54.25	$54.20
Purchase #4	$76.56	7.872%	$82.5868	$82.59	$82.60	$82.60
Purchase #5	$114.68	7.469%	$123.2454	$123.25	$123.25	$123.20
Purchase #6	$118.48	5.631%	$125.1516	$125.15	$125.15	$125.20
Purchase #7	$112.25	13.868%	$127.8168	$127.82	$127.80	$127.80
7 purchase totals =	$600.80		$652.6119	$652.62	$652.65	$652.60