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	$245.51	4.244%	$255.9294	$255.93	$255.95	$255.90
Purchase #2	$82.82	7.777%	$89.2609	$89.26	$89.25	$89.30
Purchase #3	$87.59	9.685%	$96.0731	$96.07	$96.05	$96.10
Purchase #4	$40.99	6.145%	$43.5088	$43.51	$43.50	$43.50
Purchase #5	$206.56	11.170%	$229.6328	$229.63	$229.65	$229.60
Purchase #6	$214.50	4.572%	$224.3069	$224.31	$224.30	$224.30
Purchase #7	$42.81	5.808%	$45.2964	$45.30	$45.30	$45.30
7 purchase totals =	$920.78		$984.0083	$984.01	$984.00	$984.00