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	$12.56	12.617%	$14.1447	$14.14	$14.15	$14.10
Purchase #2	$80.25	12.110%	$89.9683	$89.97	$89.95	$90.00
Purchase #3	$185.84	3.439%	$192.231	$192.23	$192.25	$192.20
Purchase #4	$193.65	10.627%	$214.2292	$214.23	$214.25	$214.20
Purchase #5	$162.66	5.424%	$171.4827	$171.48	$171.50	$171.50
Purchase #6	$40.43	12.643%	$45.5416	$45.54	$45.55	$45.50
Purchase #7	$45.67	12.253%	$51.2659	$51.27	$51.25	$51.30
7 purchase totals =	$721.06		$778.8634	$778.86	$778.90	$778.80