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	$216.92	11.326%	$241.4884	$241.49	$241.50	$241.50
Purchase #2	$13.41	7.288%	$14.3873	$14.39	$14.40	$14.40
Purchase #3	$88.46	12.490%	$99.5087	$99.51	$99.50	$99.50
Purchase #4	$130.52	11.335%	$145.3144	$145.31	$145.30	$145.30
Purchase #5	$39.93	9.849%	$43.8627	$43.86	$43.85	$43.90
Purchase #6	$28.91	7.683%	$31.1312	$31.13	$31.15	$31.10
Purchase #7	$171.36	11.241%	$190.6226	$190.62	$190.60	$190.60
7 purchase totals =	$689.51		$766.3153	$766.31	$766.30	$766.30