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	$82.64	4.346%	$86.2315	$86.23	$86.25	$86.20
Purchase #2	$160.44	9.156%	$175.1299	$175.13	$175.15	$175.10
Purchase #3	$202.41	11.173%	$225.0253	$225.03	$225.05	$225.00
Purchase #4	$80.71	10.604%	$89.2685	$89.27	$89.25	$89.30
Purchase #5	$113.52	5.238%	$119.4662	$119.47	$119.45	$119.50
Purchase #6	$224.27	11.551%	$250.1754	$250.18	$250.20	$250.20
Purchase #7	$123.48	6.561%	$131.5815	$131.58	$131.60	$131.60
7 purchase totals =	$987.47		$1,076.8783	$1,076.89	$1,076.95	$1,076.90