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	$186.27	7.500%	$200.2403	$200.24	$200.25	$200.20
Purchase #2	$149.36	10.473%	$165.0025	$165.00	$165.00	$165.00
Purchase #3	$156.55	9.426%	$171.3064	$171.31	$171.30	$171.30
Purchase #4	$238.39	11.176%	$265.0325	$265.03	$265.05	$265.00
Purchase #5	$34.27	10.517%	$37.8742	$37.87	$37.85	$37.90
Purchase #6	$31.66	3.857%	$32.8811	$32.88	$32.90	$32.90
Purchase #7	$137.63	13.722%	$156.5156	$156.52	$156.50	$156.50
7 purchase totals =	$934.13		$1,028.8526	$1,028.85	$1,028.85	$1,028.80