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	$37.75	8.408%	$40.924	$40.92	$40.90	$40.90
Purchase #2	$85.67	4.831%	$89.8087	$89.81	$89.80	$89.80
Purchase #3	$38.84	6.669%	$41.4302	$41.43	$41.45	$41.40
Purchase #4	$182.42	9.813%	$200.3209	$200.32	$200.30	$200.30
Purchase #5	$69.57	8.874%	$75.7436	$75.74	$75.75	$75.70
Purchase #6	$144.43	4.247%	$150.5639	$150.56	$150.55	$150.60
Purchase #7	$92.35	10.737%	$102.2656	$102.27	$102.25	$102.30
7 purchase totals =	$651.03		$701.0569	$701.05	$701.00	$701.00