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	$49.75	11.641%	$55.5414	$55.54	$55.55	$55.50
Purchase #2	$41.35	13.149%	$46.7871	$46.79	$46.80	$46.80
Purchase #3	$211.89	5.209%	$222.9274	$222.93	$222.95	$222.90
Purchase #4	$202.59	11.484%	$225.8554	$225.86	$225.85	$225.90
Purchase #5	$70.57	4.591%	$73.8099	$73.81	$73.80	$73.80
Purchase #6	$184.49	11.600%	$205.8908	$205.89	$205.90	$205.90
Purchase #7	$179.62	10.419%	$198.3346	$198.33	$198.35	$198.30
7 purchase totals =	$940.26		$1,029.1466	$1,029.15	$1,029.20	$1,029.10