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	$225.82	3.181%	$233.0033	$233.00	$233.00	$233.00
Purchase #2	$49.33	4.400%	$51.5005	$51.50	$51.50	$51.50
Purchase #3	$146.91	4.123%	$152.9671	$152.97	$152.95	$153.00
Purchase #4	$173.69	8.278%	$188.0681	$188.07	$188.05	$188.10
Purchase #5	$250.93	5.391%	$264.4576	$264.46	$264.45	$264.50
Purchase #6	$25.90	6.373%	$27.5506	$27.55	$27.55	$27.60
Purchase #7	$76.44	12.849%	$86.2618	$86.26	$86.25	$86.30
7 purchase totals =	$949.02		$1,003.8090	$1,003.81	$1,003.75	$1,004.00