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	$119.55	6.366%	$127.1606	$127.16	$127.15	$127.20
Purchase #2	$120.93	9.222%	$132.0822	$132.08	$132.10	$132.10
Purchase #3	$143.31	8.171%	$155.0199	$155.02	$155.00	$155.00
Purchase #4	$134.26	13.616%	$152.5408	$152.54	$152.55	$152.50
Purchase #5	$148.76	13.172%	$168.3547	$168.35	$168.35	$168.40
Purchase #6	$243.47	7.396%	$261.477	$261.48	$261.50	$261.50
Purchase #7	$37.80	12.472%	$42.5144	$42.51	$42.50	$42.50
7 purchase totals =	$948.08		$1,039.1496	$1,039.14	$1,039.15	$1,039.20