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	$88.72	6.231%	$94.2481	$94.25	$94.25	$94.20
Purchase #2	$241.97	11.528%	$269.8643	$269.86	$269.85	$269.90
Purchase #3	$208.61	7.133%	$223.4902	$223.49	$223.50	$223.50
Purchase #4	$115.82	8.630%	$125.8153	$125.82	$125.80	$125.80
Purchase #5	$181.88	12.725%	$205.0242	$205.02	$205.00	$205.00
Purchase #6	$154.93	6.357%	$164.7789	$164.78	$164.80	$164.80
Purchase #7	$188.83	8.203%	$204.3197	$204.32	$204.30	$204.30
7 purchase totals =	$1,180.76		$1,287.5407	$1,287.54	$1,287.50	$1,287.50