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	$129.85	9.203%	$141.8001	$141.80	$141.80	$141.80
Purchase #2	$132.32	6.126%	$140.4259	$140.43	$140.45	$140.40
Purchase #3	$242.85	6.654%	$259.0092	$259.01	$259.00	$259.00
Purchase #4	$126.85	5.109%	$133.3308	$133.33	$133.35	$133.30
Purchase #5	$114.89	11.316%	$127.891	$127.89	$127.90	$127.90
Purchase #6	$94.71	4.661%	$99.1244	$99.12	$99.10	$99.10
Purchase #7	$160.47	13.443%	$182.042	$182.04	$182.05	$182.00
7 purchase totals =	$1,001.94		$1,083.6234	$1,083.62	$1,083.65	$1,083.50