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	$14.54	7.494%	$15.6296	$15.63	$15.65	$15.60
Purchase #2	$173.44	13.223%	$196.374	$196.37	$196.35	$196.40
Purchase #3	$226.88	12.165%	$254.48	$254.48	$254.50	$254.50
Purchase #4	$165.33	5.842%	$174.9886	$174.99	$175.00	$175.00
Purchase #5	$156.56	9.334%	$171.1733	$171.17	$171.15	$171.20
Purchase #6	$168.69	12.273%	$189.3933	$189.39	$189.40	$189.40
Purchase #7	$217.39	11.259%	$241.8659	$241.87	$241.85	$241.90
7 purchase totals =	$1,122.83		$1,243.9047	$1,243.90	$1,243.90	$1,244.00