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	$90.93	5.130%	$95.5947	$95.59	$95.60	$95.60
Purchase #2	$100.82	13.633%	$114.5648	$114.56	$114.55	$114.60
Purchase #3	$103.41	10.768%	$114.5452	$114.55	$114.55	$114.50
Purchase #4	$172.41	10.104%	$189.8303	$189.83	$189.85	$189.80
Purchase #5	$28.69	8.385%	$31.0957	$31.10	$31.10	$31.10
Purchase #6	$107.44	10.793%	$119.036	$119.04	$119.05	$119.00
Purchase #7	$62.79	7.862%	$67.7265	$67.73	$67.75	$67.70
7 purchase totals =	$666.49		$732.3932	$732.40	$732.45	$732.30