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	$98.81	10.666%	$109.3491	$109.35	$109.35	$109.30
Purchase #2	$238.90	6.274%	$253.8886	$253.89	$253.90	$253.90
Purchase #3	$84.27	11.738%	$94.1616	$94.16	$94.15	$94.20
Purchase #4	$112.95	11.786%	$126.2623	$126.26	$126.25	$126.30
Purchase #5	$126.36	4.616%	$132.1928	$132.19	$132.20	$132.20
Purchase #6	$196.99	6.866%	$210.5153	$210.52	$210.50	$210.50
Purchase #7	$118.84	3.756%	$123.3036	$123.30	$123.30	$123.30
7 purchase totals =	$977.12		$1,049.6733	$1,049.67	$1,049.65	$1,049.70