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	$225.97	7.672%	$243.3064	$243.31	$243.30	$243.30
Purchase #2	$194.42	7.301%	$208.6146	$208.61	$208.60	$208.60
Purchase #3	$128.72	11.337%	$143.313	$143.31	$143.30	$143.30
Purchase #4	$50.44	3.304%	$52.1065	$52.11	$52.10	$52.10
Purchase #5	$190.82	3.275%	$197.0694	$197.07	$197.05	$197.10
Purchase #6	$87.58	13.630%	$99.5172	$99.52	$99.50	$99.50
Purchase #7	$105.36	6.543%	$112.2537	$112.25	$112.25	$112.30
7 purchase totals =	$983.31		$1,056.1808	$1,056.18	$1,056.10	$1,056.20