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	$55.80	13.389%	$63.2711	$63.27	$63.25	$63.30
Purchase #2	$91.42	13.715%	$103.9583	$103.96	$103.95	$104.00
Purchase #3	$213.89	4.379%	$223.2562	$223.26	$223.25	$223.30
Purchase #4	$44.69	12.727%	$50.3777	$50.38	$50.40	$50.40
Purchase #5	$94.41	9.756%	$103.6206	$103.62	$103.60	$103.60
Purchase #6	$98.47	9.821%	$108.1407	$108.14	$108.15	$108.10
Purchase #7	$110.91	4.151%	$115.5139	$115.51	$115.50	$115.50
7 purchase totals =	$709.59		$768.1385	$768.14	$768.10	$768.20