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	$237.83	7.355%	$255.3224	$255.32	$255.30	$255.30
Purchase #2	$150.56	9.554%	$164.9445	$164.94	$164.95	$164.90
Purchase #3	$40.57	7.635%	$43.6675	$43.67	$43.65	$43.70
Purchase #4	$46.90	4.283%	$48.9087	$48.91	$48.90	$48.90
Purchase #5	$229.92	11.181%	$255.6274	$255.63	$255.65	$255.60
Purchase #6	$242.52	9.832%	$266.3646	$266.36	$266.35	$266.40
Purchase #7	$145.47	9.469%	$159.2446	$159.24	$159.25	$159.20
7 purchase totals =	$1,093.77		$1,194.0797	$1,194.07	$1,194.05	$1,194.00