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	$233.34	9.691%	$255.953	$255.95	$255.95	$256.00
Purchase #2	$157.33	5.471%	$165.9375	$165.94	$165.95	$165.90
Purchase #3	$219.43	5.558%	$231.6259	$231.63	$231.65	$231.60
Purchase #4	$206.40	7.809%	$222.5178	$222.52	$222.50	$222.50
Purchase #5	$44.53	5.323%	$46.9003	$46.90	$46.90	$46.90
Purchase #6	$102.92	5.775%	$108.8636	$108.86	$108.85	$108.90
Purchase #7	$183.33	3.799%	$190.2947	$190.29	$190.30	$190.30
7 purchase totals =	$1,147.28		$1,222.0928	$1,222.09	$1,222.10	$1,222.10