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	$79.37	8.123%	$85.8172	$85.82	$85.80	$85.80
Purchase #2	$64.31	8.344%	$69.676	$69.68	$69.70	$69.70
Purchase #3	$171.82	5.475%	$181.2271	$181.23	$181.25	$181.20
Purchase #4	$157.57	11.387%	$175.5125	$175.51	$175.50	$175.50
Purchase #5	$146.74	4.133%	$152.8048	$152.80	$152.80	$152.80
Purchase #6	$56.54	4.676%	$59.1838	$59.18	$59.20	$59.20
Purchase #7	$54.81	8.457%	$59.4453	$59.45	$59.45	$59.40
7 purchase totals =	$731.16		$783.6667	$783.67	$783.70	$783.60