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	$136.37	7.252%	$146.2596	$146.26	$146.25	$146.30
Purchase #2	$51.98	5.708%	$54.947	$54.95	$54.95	$54.90
Purchase #3	$98.56	7.441%	$105.8938	$105.89	$105.90	$105.90
Purchase #4	$157.93	9.399%	$172.7738	$172.77	$172.75	$172.80
Purchase #5	$90.87	5.459%	$95.8306	$95.83	$95.85	$95.80
Purchase #6	$186.98	9.612%	$204.9525	$204.95	$204.95	$205.00
Purchase #7	$85.68	10.721%	$94.8658	$94.87	$94.85	$94.90
7 purchase totals =	$808.37		$875.5231	$875.52	$875.50	$875.60