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	$133.74	9.195%	$146.0374	$146.04	$146.05	$146.00
Purchase #2	$112.28	9.626%	$123.0881	$123.09	$123.10	$123.10
Purchase #3	$138.79	7.272%	$148.8828	$148.88	$148.90	$148.90
Purchase #4	$166.73	12.780%	$188.0381	$188.04	$188.05	$188.00
Purchase #5	$28.82	10.151%	$31.7455	$31.75	$31.75	$31.70
Purchase #6	$126.69	5.404%	$133.5363	$133.54	$133.55	$133.50
Purchase #7	$86.33	13.552%	$98.0294	$98.03	$98.05	$98.00
7 purchase totals =	$793.38		$869.3576	$869.37	$869.45	$869.20