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	$213.52	11.779%	$238.6705	$238.67	$238.65	$238.70
Purchase #2	$74.27	7.683%	$79.9762	$79.98	$80.00	$80.00
Purchase #3	$191.51	12.795%	$216.0137	$216.01	$216.00	$216.00
Purchase #4	$185.86	11.625%	$207.4662	$207.47	$207.45	$207.50
Purchase #5	$78.43	5.431%	$82.6895	$82.69	$82.70	$82.70
Purchase #6	$144.91	13.736%	$164.8148	$164.81	$164.80	$164.80
Purchase #7	$12.52	3.260%	$12.9282	$12.93	$12.95	$12.90
7 purchase totals =	$901.02		$1,002.5591	$1,002.56	$1,002.55	$1,002.60