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	$214.73	11.500%	$239.424	$239.42	$239.40	$239.40
Purchase #2	$54.89	11.171%	$61.0218	$61.02	$61.00	$61.00
Purchase #3	$171.89	3.593%	$178.066	$178.07	$178.05	$178.10
Purchase #4	$179.78	3.560%	$186.1802	$186.18	$186.20	$186.20
Purchase #5	$205.67	11.494%	$229.3097	$229.31	$229.30	$229.30
Purchase #6	$138.76	12.831%	$156.5643	$156.56	$156.55	$156.60
Purchase #7	$51.26	5.257%	$53.9547	$53.95	$53.95	$54.00
7 purchase totals =	$1,016.98		$1,104.5207	$1,104.51	$1,104.45	$1,104.60