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	$97.96	5.773%	$103.6152	$103.62	$103.60	$103.60
Purchase #2	$14.46	3.783%	$15.007	$15.01	$15.00	$15.00
Purchase #3	$39.94	11.180%	$44.4053	$44.41	$44.40	$44.40
Purchase #4	$206.51	7.685%	$222.3803	$222.38	$222.40	$222.40
Purchase #5	$110.25	3.786%	$114.4241	$114.42	$114.40	$114.40
Purchase #6	$146.76	7.219%	$157.3546	$157.35	$157.35	$157.40
Purchase #7	$100.27	8.528%	$108.821	$108.82	$108.80	$108.80
7 purchase totals =	$716.15		$766.0075	$766.01	$765.95	$766.00