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	$76.35	9.342%	$83.4826	$83.48	$83.50	$83.50
Purchase #2	$34.63	4.397%	$36.1527	$36.15	$36.15	$36.20
Purchase #3	$46.54	10.788%	$51.5607	$51.56	$51.55	$51.60
Purchase #4	$8.59	3.839%	$8.9198	$8.92	$8.90	$8.90
Purchase #5	$243.84	4.780%	$255.4956	$255.50	$255.50	$255.50
Purchase #6	$177.33	4.469%	$185.2549	$185.25	$185.25	$185.30
Purchase #7	$7.89	9.748%	$8.6591	$8.66	$8.65	$8.70
7 purchase totals =	$595.17		$629.5254	$629.52	$629.50	$629.70