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	$157.38	5.124%	$165.4442	$165.44	$165.45	$165.40
Purchase #2	$247.27	7.532%	$265.8944	$265.89	$265.90	$265.90
Purchase #3	$180.47	8.719%	$196.2052	$196.21	$196.20	$196.20
Purchase #4	$212.88	6.151%	$225.9742	$225.97	$225.95	$226.00
Purchase #5	$118.69	11.657%	$132.5257	$132.53	$132.55	$132.50
Purchase #6	$71.58	10.255%	$78.9205	$78.92	$78.90	$78.90
Purchase #7	$11.50	8.424%	$12.4688	$12.47	$12.45	$12.50
7 purchase totals =	$999.77		$1,077.4330	$1,077.43	$1,077.40	$1,077.40