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	$49.68	13.382%	$56.3282	$56.33	$56.35	$56.30
Purchase #2	$179.98	4.173%	$187.4906	$187.49	$187.50	$187.50
Purchase #3	$41.98	9.555%	$45.9912	$45.99	$46.00	$46.00
Purchase #4	$72.37	8.232%	$78.3275	$78.33	$78.35	$78.30
Purchase #5	$12.34	4.308%	$12.8716	$12.87	$12.85	$12.90
Purchase #6	$142.87	12.347%	$160.5102	$160.51	$160.50	$160.50
Purchase #7	$31.52	4.654%	$32.9869	$32.99	$33.00	$33.00
7 purchase totals =	$530.74		$574.5062	$574.51	$574.55	$574.50