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	$126.57	11.812%	$141.5204	$141.52	$141.50	$141.50
Purchase #2	$59.73	12.233%	$67.0368	$67.04	$67.05	$67.00
Purchase #3	$140.47	11.286%	$156.3234	$156.32	$156.30	$156.30
Purchase #4	$12.79	5.854%	$13.5387	$13.54	$13.55	$13.50
Purchase #5	$212.80	7.296%	$228.3259	$228.33	$228.35	$228.30
Purchase #6	$171.56	12.775%	$193.4768	$193.48	$193.50	$193.50
Purchase #7	$242.65	9.312%	$265.2456	$265.25	$265.25	$265.20
7 purchase totals =	$966.57		$1,065.4676	$1,065.48	$1,065.50	$1,065.30