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	$76.93	12.498%	$86.5447	$86.54	$86.55	$86.50
Purchase #2	$114.26	11.370%	$127.2514	$127.25	$127.25	$127.30
Purchase #3	$196.36	7.872%	$211.8175	$211.82	$211.80	$211.80
Purchase #4	$41.56	4.847%	$43.5744	$43.57	$43.55	$43.60
Purchase #5	$206.65	12.756%	$233.0103	$233.01	$233.00	$233.00
Purchase #6	$217.26	7.540%	$233.6414	$233.64	$233.65	$233.60
Purchase #7	$204.34	10.462%	$225.7181	$225.72	$225.70	$225.70
7 purchase totals =	$1,057.36		$1,161.5578	$1,161.55	$1,161.50	$1,161.50