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	$241.88	9.471%	$264.7885	$264.79	$264.80	$264.80
Purchase #2	$13.54	8.259%	$14.6583	$14.66	$14.65	$14.70
Purchase #3	$195.30	11.280%	$217.3298	$217.33	$217.35	$217.30
Purchase #4	$20.63	3.684%	$21.39	$21.39	$21.40	$21.40
Purchase #5	$67.59	4.376%	$70.5477	$70.55	$70.55	$70.50
Purchase #6	$36.85	7.469%	$39.6023	$39.60	$39.60	$39.60
Purchase #7	$136.48	11.212%	$151.7821	$151.78	$151.80	$151.80
7 purchase totals =	$712.27		$780.0987	$780.10	$780.15	$780.10