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	$245.70	3.762%	$254.9432	$254.94	$254.95	$254.90
Purchase #2	$54.44	13.591%	$61.8389	$61.84	$61.85	$61.80
Purchase #3	$144.61	12.290%	$162.3826	$162.38	$162.40	$162.40
Purchase #4	$43.29	3.629%	$44.861	$44.86	$44.85	$44.90
Purchase #5	$117.78	11.258%	$131.0397	$131.04	$131.05	$131.00
Purchase #6	$12.90	8.442%	$13.989	$13.99	$14.00	$14.00
Purchase #7	$190.75	11.407%	$212.5089	$212.51	$212.50	$212.50
7 purchase totals =	$809.47		$881.5633	$881.56	$881.60	$881.50