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	$176.60	12.629%	$198.9028	$198.90	$198.90	$198.90
Purchase #2	$245.62	5.474%	$259.0652	$259.07	$259.05	$259.10
Purchase #3	$30.56	6.539%	$32.5583	$32.56	$32.55	$32.60
Purchase #4	$171.66	6.131%	$182.1845	$182.18	$182.20	$182.20
Purchase #5	$112.78	12.512%	$126.891	$126.89	$126.90	$126.90
Purchase #6	$73.29	7.351%	$78.6775	$78.68	$78.70	$78.70
Purchase #7	$111.89	13.708%	$127.2279	$127.23	$127.25	$127.20
7 purchase totals =	$922.40		$1,005.5072	$1,005.51	$1,005.55	$1,005.60