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	$166.49	8.751%	$181.0595	$181.06	$181.05	$181.10
Purchase #2	$187.56	13.492%	$212.8656	$212.87	$212.85	$212.90
Purchase #3	$10.62	13.377%	$12.0406	$12.04	$12.05	$12.00
Purchase #4	$213.34	8.634%	$231.7598	$231.76	$231.75	$231.80
Purchase #5	$172.89	10.755%	$191.4843	$191.48	$191.50	$191.50
Purchase #6	$178.44	4.102%	$185.7596	$185.76	$185.75	$185.80
Purchase #7	$82.73	9.664%	$90.725	$90.73	$90.75	$90.70
7 purchase totals =	$1,012.07		$1,105.6944	$1,105.70	$1,105.70	$1,105.80