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	$137.66	10.607%	$152.2616	$152.26	$152.25	$152.30
Purchase #2	$31.98	7.573%	$34.4018	$34.40	$34.40	$34.40
Purchase #3	$63.55	13.747%	$72.2862	$72.29	$72.30	$72.30
Purchase #4	$171.65	5.765%	$181.5456	$181.55	$181.55	$181.50
Purchase #5	$217.65	12.218%	$244.2425	$244.24	$244.25	$244.20
Purchase #6	$214.88	4.660%	$224.8934	$224.89	$224.90	$224.90
Purchase #7	$150.44	10.504%	$166.2422	$166.24	$166.25	$166.20
7 purchase totals =	$987.81		$1,075.8733	$1,075.87	$1,075.90	$1,075.80