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	$169.27	13.716%	$192.4871	$192.49	$192.50	$192.50
Purchase #2	$52.89	6.716%	$56.4421	$56.44	$56.45	$56.40
Purchase #3	$238.49	4.367%	$248.9049	$248.90	$248.90	$248.90
Purchase #4	$93.31	10.295%	$102.9163	$102.92	$102.90	$102.90
Purchase #5	$39.55	10.107%	$43.5473	$43.55	$43.55	$43.50
Purchase #6	$169.44	7.384%	$181.9514	$181.95	$181.95	$182.00
Purchase #7	$214.60	4.180%	$223.5703	$223.57	$223.55	$223.60
7 purchase totals =	$977.55		$1,049.8194	$1,049.82	$1,049.80	$1,049.80