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	$131.46	10.420%	$145.1581	$145.16	$145.15	$145.20
Purchase #2	$109.38	9.274%	$119.5239	$119.52	$119.50	$119.50
Purchase #3	$86.69	3.217%	$89.4788	$89.48	$89.50	$89.50
Purchase #4	$84.26	11.458%	$93.9145	$93.91	$93.90	$93.90
Purchase #5	$142.87	11.713%	$159.6044	$159.60	$159.60	$159.60
Purchase #6	$223.72	10.507%	$247.2263	$247.23	$247.25	$247.20
Purchase #7	$114.47	11.223%	$127.317	$127.32	$127.30	$127.30
7 purchase totals =	$892.85		$982.2230	$982.22	$982.20	$982.20