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	$211.66	5.326%	$222.933	$222.93	$222.95	$222.90
Purchase #2	$90.41	4.529%	$94.5047	$94.50	$94.50	$94.50
Purchase #3	$218.57	3.628%	$226.4997	$226.50	$226.50	$226.50
Purchase #4	$148.94	6.786%	$159.0471	$159.05	$159.05	$159.00
Purchase #5	$105.61	12.819%	$119.1481	$119.15	$119.15	$119.10
Purchase #6	$41.46	3.316%	$42.8348	$42.83	$42.85	$42.80
Purchase #7	$83.30	9.291%	$91.0394	$91.04	$91.05	$91.00
7 purchase totals =	$899.95		$956.0068	$956.00	$956.05	$955.80