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	$174.98	7.175%	$187.5348	$187.53	$187.55	$187.50
Purchase #2	$200.69	7.363%	$215.4668	$215.47	$215.45	$215.50
Purchase #3	$134.52	4.862%	$141.0604	$141.06	$141.05	$141.10
Purchase #4	$102.29	9.124%	$111.6229	$111.62	$111.60	$111.60
Purchase #5	$249.48	13.384%	$282.8704	$282.87	$282.85	$282.90
Purchase #6	$11.50	11.534%	$12.8264	$12.83	$12.85	$12.80
Purchase #7	$250.85	7.410%	$269.438	$269.44	$269.45	$269.40
7 purchase totals =	$1,124.31		$1,220.8197	$1,220.82	$1,220.80	$1,220.80