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	$149.82	5.107%	$157.4713	$157.47	$157.45	$157.50
Purchase #2	$95.55	7.197%	$102.4267	$102.43	$102.45	$102.40
Purchase #3	$205.88	4.671%	$215.4967	$215.50	$215.50	$215.50
Purchase #4	$98.66	5.331%	$103.9196	$103.92	$103.90	$103.90
Purchase #5	$220.35	3.461%	$227.9763	$227.98	$228.00	$228.00
Purchase #6	$120.76	6.549%	$128.6686	$128.67	$128.65	$128.70
Purchase #7	$37.66	11.798%	$42.1031	$42.10	$42.10	$42.10
7 purchase totals =	$928.68		$978.0623	$978.07	$978.05	$978.10