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	$72.55	13.848%	$82.5967	$82.60	$82.60	$82.60
Purchase #2	$22.36	9.396%	$24.4609	$24.46	$24.45	$24.50
Purchase #3	$77.68	6.375%	$82.6321	$82.63	$82.65	$82.60
Purchase #4	$28.92	13.771%	$32.9026	$32.90	$32.90	$32.90
Purchase #5	$128.62	3.855%	$133.5783	$133.58	$133.60	$133.60
Purchase #6	$69.26	6.812%	$73.978	$73.98	$74.00	$74.00
Purchase #7	$198.63	6.274%	$211.092	$211.09	$211.10	$211.10
7 purchase totals =	$598.02		$641.2406	$641.24	$641.30	$641.30