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	$118.70	10.353%	$130.989	$130.99	$131.00	$131.00
Purchase #2	$159.62	7.324%	$171.3106	$171.31	$171.30	$171.30
Purchase #3	$196.62	7.261%	$210.8966	$210.90	$210.90	$210.90
Purchase #4	$13.88	7.169%	$14.8751	$14.88	$14.90	$14.90
Purchase #5	$222.51	8.493%	$241.4078	$241.41	$241.40	$241.40
Purchase #6	$123.93	3.129%	$127.8078	$127.81	$127.80	$127.80
Purchase #7	$129.32	6.119%	$137.2331	$137.23	$137.25	$137.20
7 purchase totals =	$964.58		$1,034.5200	$1,034.53	$1,034.55	$1,034.50